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<div class="section" id="module-venv">
<span id="venv-creation-of-virtual-environments"></span><h1><a class="reference internal" href="#module-venv" title="venv: Creation of virtual environments."><code class="xref py py-mod docutils literal notranslate"><span class="pre">venv</span></code></a> — Creation of virtual environments<a class="headerlink" href="#module-venv" title="Permalink to this headline">¶</a></h1>
<div class="versionadded">
<p><span class="versionmodified added">New in version 3.3.</span></p>
</div>
<p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.7/Lib/venv/">Lib/venv/</a></p>
<hr class="docutils" id="index-0" />
<p>The <a class="reference internal" href="#module-venv" title="venv: Creation of virtual environments."><code class="xref py py-mod docutils literal notranslate"><span class="pre">venv</span></code></a> module provides support for creating lightweight “virtual
environments” with their own site directories, optionally isolated from system
site directories. Each virtual environment has its own Python binary (which
matches the version of the binary that was used to create this environment) and
can have its own independent set of installed Python packages in its site
directories.</p>
<p>See <span class="target" id="index-1"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0405"><strong>PEP 405</strong></a> for more information about Python virtual environments.</p>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference external" href="https://packaging.python.org/installing/#creating-virtual-environments">Python Packaging User Guide: Creating and using virtual environments</a></p>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <code class="docutils literal notranslate"><span class="pre">pyvenv</span></code> script has been deprecated as of Python 3.6 in favor of using
<code class="docutils literal notranslate"><span class="pre">python3</span> <span class="pre">-m</span> <span class="pre">venv</span></code> to help prevent any potential confusion as to which
Python interpreter a virtual environment will be based on.</p>
</div>
<div class="section" id="creating-virtual-environments">
<h2>Creating virtual environments<a class="headerlink" href="#creating-virtual-environments" title="Permalink to this headline">¶</a></h2>
<p>Creation of <a class="reference internal" href="#venv-def"><span class="std std-ref">virtual environments</span></a> is done by executing the
command <code class="docutils literal notranslate"><span class="pre">venv</span></code>:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">python3</span> <span class="o">-</span><span class="n">m</span> <span class="n">venv</span> <span class="o">/</span><span class="n">path</span><span class="o">/</span><span class="n">to</span><span class="o">/</span><span class="n">new</span><span class="o">/</span><span class="n">virtual</span><span class="o">/</span><span class="n">environment</span>
</pre></div>
</div>
<p>Running this command creates the target directory (creating any parent
directories that don’t exist already) and places a <code class="docutils literal notranslate"><span class="pre">pyvenv.cfg</span></code> file in it
with a <code class="docutils literal notranslate"><span class="pre">home</span></code> key pointing to the Python installation from which the command
was run. It also creates a <code class="docutils literal notranslate"><span class="pre">bin</span></code> (or <code class="docutils literal notranslate"><span class="pre">Scripts</span></code> on Windows) subdirectory
containing a copy/symlink of the Python binary/binaries (as appropriate for the
platform or arguments used at environment creation time). It also creates an
(initially empty) <code class="docutils literal notranslate"><span class="pre">lib/pythonX.Y/site-packages</span></code> subdirectory
(on Windows, this is <code class="docutils literal notranslate"><span class="pre">Lib\site-packages</span></code>). If an existing
directory is specified, it will be re-used.</p>
<div class="deprecated">
<p><span class="versionmodified deprecated">Deprecated since version 3.6: </span><code class="docutils literal notranslate"><span class="pre">pyvenv</span></code> was the recommended tool for creating virtual environments for
Python 3.3 and 3.4, and is <a class="reference external" href="https://docs.python.org/dev/whatsnew/3.6.html#deprecated-features">deprecated in Python 3.6</a>.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.5: </span>The use of <code class="docutils literal notranslate"><span class="pre">venv</span></code> is now recommended for creating virtual environments.</p>
</div>
<p>On Windows, invoke the <code class="docutils literal notranslate"><span class="pre">venv</span></code> command as follows:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>c:\>c:\Python35\python -m venv c:\path\to\myenv
</pre></div>
</div>
<p>Alternatively, if you configured the <code class="docutils literal notranslate"><span class="pre">PATH</span></code> and <code class="docutils literal notranslate"><span class="pre">PATHEXT</span></code> variables for
your <a class="reference internal" href="../using/windows.html#using-on-windows"><span class="std std-ref">Python installation</span></a>:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>c:\>python -m venv c:\path\to\myenv
</pre></div>
</div>
<p>The command, if run with <code class="docutils literal notranslate"><span class="pre">-h</span></code>, will show the available options:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>usage: venv [-h] [--system-site-packages] [--symlinks | --copies] [--clear]
[--upgrade] [--without-pip] [--prompt PROMPT]
ENV_DIR [ENV_DIR ...]
Creates virtual Python environments in one or more target directories.
positional arguments:
ENV_DIR A directory to create the environment in.
optional arguments:
-h, --help show this help message and exit
--system-site-packages
Give the virtual environment access to the system
site-packages dir.
--symlinks Try to use symlinks rather than copies, when symlinks
are not the default for the platform.
--copies Try to use copies rather than symlinks, even when
symlinks are the default for the platform.
--clear Delete the contents of the environment directory if it
already exists, before environment creation.
--upgrade Upgrade the environment directory to use this version
of Python, assuming Python has been upgraded in-place.
--without-pip Skips installing or upgrading pip in the virtual
environment (pip is bootstrapped by default)
--prompt PROMPT Provides an alternative prompt prefix for this
environment.
Once an environment has been created, you may wish to activate it, e.g. by
sourcing an activate script in its bin directory.
</pre></div>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.4: </span>Installs pip by default, added the <code class="docutils literal notranslate"><span class="pre">--without-pip</span></code> and <code class="docutils literal notranslate"><span class="pre">--copies</span></code>
options</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.4: </span>In earlier versions, if the target directory already existed, an error was
raised, unless the <code class="docutils literal notranslate"><span class="pre">--clear</span></code> or <code class="docutils literal notranslate"><span class="pre">--upgrade</span></code> option was provided.</p>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>While symlinks are supported on Windows, they are not recommended. Of
particular note is that double-clicking <code class="docutils literal notranslate"><span class="pre">python.exe</span></code> in File Explorer
will resolve the symlink eagerly and ignore the virtual environment.</p>
</div>
<p>The created <code class="docutils literal notranslate"><span class="pre">pyvenv.cfg</span></code> file also includes the
<code class="docutils literal notranslate"><span class="pre">include-system-site-packages</span></code> key, set to <code class="docutils literal notranslate"><span class="pre">true</span></code> if <code class="docutils literal notranslate"><span class="pre">venv</span></code> is
run with the <code class="docutils literal notranslate"><span class="pre">--system-site-packages</span></code> option, <code class="docutils literal notranslate"><span class="pre">false</span></code> otherwise.</p>
<p>Unless the <code class="docutils literal notranslate"><span class="pre">--without-pip</span></code> option is given, <a class="reference internal" href="ensurepip.html#module-ensurepip" title="ensurepip: Bootstrapping the "pip" installer into an existing Python installation or virtual environment."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ensurepip</span></code></a> will be
invoked to bootstrap <code class="docutils literal notranslate"><span class="pre">pip</span></code> into the virtual environment.</p>
<p>Multiple paths can be given to <code class="docutils literal notranslate"><span class="pre">venv</span></code>, in which case an identical virtual
environment will be created, according to the given options, at each provided
path.</p>
<p>Once a virtual environment has been created, it can be “activated” using a
script in the virtual environment’s binary directory. The invocation of the
script is platform-specific (<cite><venv></cite> must be replaced by the path of the
directory containing the virtual environment):</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 18%" />
<col style="width: 24%" />
<col style="width: 58%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>Platform</p></th>
<th class="head"><p>Shell</p></th>
<th class="head"><p>Command to activate virtual environment</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>Posix</p></td>
<td><p>bash/zsh</p></td>
<td><p>$ source <venv>/bin/activate</p></td>
</tr>
<tr class="row-odd"><td></td>
<td><p>fish</p></td>
<td><p>$ . <venv>/bin/activate.fish</p></td>
</tr>
<tr class="row-even"><td></td>
<td><p>csh/tcsh</p></td>
<td><p>$ source <venv>/bin/activate.csh</p></td>
</tr>
<tr class="row-odd"><td><p>Windows</p></td>
<td><p>cmd.exe</p></td>
<td><p>C:\> <venv>\Scripts\activate.bat</p></td>
</tr>
<tr class="row-even"><td></td>
<td><p>PowerShell</p></td>
<td><p>PS C:\> <venv>\Scripts\Activate.ps1</p></td>
</tr>
</tbody>
</table>
<p>You don’t specifically <em>need</em> to activate an environment; activation just
prepends the virtual environment’s binary directory to your path, so that
“python” invokes the virtual environment’s Python interpreter and you can run
installed scripts without having to use their full path. However, all scripts
installed in a virtual environment should be runnable without activating it,
and run with the virtual environment’s Python automatically.</p>
<p>You can deactivate a virtual environment by typing “deactivate” in your shell.
The exact mechanism is platform-specific and is an internal implementation
detail (typically a script or shell function will be used).</p>
<div class="versionadded">
<p><span class="versionmodified added">New in version 3.4: </span><code class="docutils literal notranslate"><span class="pre">fish</span></code> and <code class="docutils literal notranslate"><span class="pre">csh</span></code> activation scripts.</p>
</div>
<div class="admonition note" id="venv-def">
<p class="admonition-title">Note</p>
<p>A virtual environment is a Python environment such that the Python
interpreter, libraries and scripts installed into it are isolated from those
installed in other virtual environments, and (by default) any libraries
installed in a “system” Python, i.e., one which is installed as part of your
operating system.</p>
<p>A virtual environment is a directory tree which contains Python executable
files and other files which indicate that it is a virtual environment.</p>
<p>Common installation tools such as <a class="reference external" href="https://pypi.org/project/setuptools/">setuptools</a> and <a class="reference external" href="https://pypi.org/project/pip/">pip</a> work as
expected with virtual environments. In other words, when a virtual
environment is active, they install Python packages into the virtual
environment without needing to be told to do so explicitly.</p>
<p>When a virtual environment is active (i.e., the virtual environment’s Python
interpreter is running), the attributes <a class="reference internal" href="sys.html#sys.prefix" title="sys.prefix"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.prefix</span></code></a> and
<a class="reference internal" href="sys.html#sys.exec_prefix" title="sys.exec_prefix"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.exec_prefix</span></code></a> point to the base directory of the virtual
environment, whereas <a class="reference internal" href="sys.html#sys.base_prefix" title="sys.base_prefix"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.base_prefix</span></code></a> and
<a class="reference internal" href="sys.html#sys.base_exec_prefix" title="sys.base_exec_prefix"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.base_exec_prefix</span></code></a> point to the non-virtual environment Python
installation which was used to create the virtual environment. If a virtual
environment is not active, then <a class="reference internal" href="sys.html#sys.prefix" title="sys.prefix"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.prefix</span></code></a> is the same as
<a class="reference internal" href="sys.html#sys.base_prefix" title="sys.base_prefix"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.base_prefix</span></code></a> and <a class="reference internal" href="sys.html#sys.exec_prefix" title="sys.exec_prefix"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.exec_prefix</span></code></a> is the same as
<a class="reference internal" href="sys.html#sys.base_exec_prefix" title="sys.base_exec_prefix"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.base_exec_prefix</span></code></a> (they all point to a non-virtual environment
Python installation).</p>
<p>When a virtual environment is active, any options that change the
installation path will be ignored from all <a class="reference internal" href="distutils.html#module-distutils" title="distutils: Support for building and installing Python modules into an existing Python installation."><code class="xref py py-mod docutils literal notranslate"><span class="pre">distutils</span></code></a> configuration
files to prevent projects being inadvertently installed outside of the
virtual environment.</p>
<p>When working in a command shell, users can make a virtual environment active
by running an <code class="docutils literal notranslate"><span class="pre">activate</span></code> script in the virtual environment’s executables
directory (the precise filename and command to use the file is
shell-dependent), which prepends the virtual environment’s directory for
executables to the <code class="docutils literal notranslate"><span class="pre">PATH</span></code> environment variable for the running shell. There
should be no need in other circumstances to activate a virtual
environment; scripts installed into virtual environments have a “shebang”
line which points to the virtual environment’s Python interpreter. This means
that the script will run with that interpreter regardless of the value of
<code class="docutils literal notranslate"><span class="pre">PATH</span></code>. On Windows, “shebang” line processing is supported if you have the
Python Launcher for Windows installed (this was added to Python in 3.3 - see
<span class="target" id="index-2"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0397"><strong>PEP 397</strong></a> for more details). Thus, double-clicking an installed script in a
Windows Explorer window should run the script with the correct interpreter
without there needing to be any reference to its virtual environment in
<code class="docutils literal notranslate"><span class="pre">PATH</span></code>.</p>
</div>
</div>
<div class="section" id="api">
<span id="venv-api"></span><h2>API<a class="headerlink" href="#api" title="Permalink to this headline">¶</a></h2>
<p>The high-level method described above makes use of a simple API which provides
mechanisms for third-party virtual environment creators to customize environment
creation according to their needs, the <a class="reference internal" href="#venv.EnvBuilder" title="venv.EnvBuilder"><code class="xref py py-class docutils literal notranslate"><span class="pre">EnvBuilder</span></code></a> class.</p>
<dl class="class">
<dt id="venv.EnvBuilder">
<em class="property">class </em><code class="sig-prename descclassname">venv.</code><code class="sig-name descname">EnvBuilder</code><span class="sig-paren">(</span><em class="sig-param">system_site_packages=False</em>, <em class="sig-param">clear=False</em>, <em class="sig-param">symlinks=False</em>, <em class="sig-param">upgrade=False</em>, <em class="sig-param">with_pip=False</em>, <em class="sig-param">prompt=None</em><span class="sig-paren">)</span><a class="headerlink" href="#venv.EnvBuilder" title="Permalink to this definition">¶</a></dt>
<dd><p>The <a class="reference internal" href="#venv.EnvBuilder" title="venv.EnvBuilder"><code class="xref py py-class docutils literal notranslate"><span class="pre">EnvBuilder</span></code></a> class accepts the following keyword arguments on
instantiation:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">system_site_packages</span></code> – a Boolean value indicating that the system Python
site-packages should be available to the environment (defaults to <code class="docutils literal notranslate"><span class="pre">False</span></code>).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">clear</span></code> – a Boolean value which, if true, will delete the contents of
any existing target directory, before creating the environment.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">symlinks</span></code> – a Boolean value indicating whether to attempt to symlink the
Python binary rather than copying.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">upgrade</span></code> – a Boolean value which, if true, will upgrade an existing
environment with the running Python - for use when that Python has been
upgraded in-place (defaults to <code class="docutils literal notranslate"><span class="pre">False</span></code>).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">with_pip</span></code> – a Boolean value which, if true, ensures pip is
installed in the virtual environment. This uses <a class="reference internal" href="ensurepip.html#module-ensurepip" title="ensurepip: Bootstrapping the "pip" installer into an existing Python installation or virtual environment."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ensurepip</span></code></a> with
the <code class="docutils literal notranslate"><span class="pre">--default-pip</span></code> option.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">prompt</span></code> – a String to be used after virtual environment is activated
(defaults to <code class="docutils literal notranslate"><span class="pre">None</span></code> which means directory name of the environment would
be used).</p></li>
</ul>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.4: </span>Added the <code class="docutils literal notranslate"><span class="pre">with_pip</span></code> parameter</p>
</div>
<div class="versionadded">
<p><span class="versionmodified added">New in version 3.6: </span>Added the <code class="docutils literal notranslate"><span class="pre">prompt</span></code> parameter</p>
</div>
<p>Creators of third-party virtual environment tools will be free to use the
provided <a class="reference internal" href="#venv.EnvBuilder" title="venv.EnvBuilder"><code class="xref py py-class docutils literal notranslate"><span class="pre">EnvBuilder</span></code></a> class as a base class.</p>
<p>The returned env-builder is an object which has a method, <code class="docutils literal notranslate"><span class="pre">create</span></code>:</p>
<dl class="method">
<dt id="venv.EnvBuilder.create">
<code class="sig-name descname">create</code><span class="sig-paren">(</span><em class="sig-param">env_dir</em><span class="sig-paren">)</span><a class="headerlink" href="#venv.EnvBuilder.create" title="Permalink to this definition">¶</a></dt>
<dd><p>Create a virtual environment by specifying the target directory
(absolute or relative to the current directory) which is to contain the
virtual environment. The <code class="docutils literal notranslate"><span class="pre">create</span></code> method will either create the
environment in the specified directory, or raise an appropriate
exception.</p>
<p>The <code class="docutils literal notranslate"><span class="pre">create</span></code> method of the <a class="reference internal" href="#venv.EnvBuilder" title="venv.EnvBuilder"><code class="xref py py-class docutils literal notranslate"><span class="pre">EnvBuilder</span></code></a> class illustrates the
hooks available for subclass customization:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">create</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">env_dir</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Create a virtualized Python environment in a directory.</span>
<span class="sd"> env_dir is the target directory to create an environment in.</span>
<span class="sd"> """</span>
<span class="n">env_dir</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">abspath</span><span class="p">(</span><span class="n">env_dir</span><span class="p">)</span>
<span class="n">context</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">ensure_directories</span><span class="p">(</span><span class="n">env_dir</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">create_configuration</span><span class="p">(</span><span class="n">context</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">setup_python</span><span class="p">(</span><span class="n">context</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">setup_scripts</span><span class="p">(</span><span class="n">context</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">post_setup</span><span class="p">(</span><span class="n">context</span><span class="p">)</span>
</pre></div>
</div>
<p>Each of the methods <a class="reference internal" href="#venv.EnvBuilder.ensure_directories" title="venv.EnvBuilder.ensure_directories"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ensure_directories()</span></code></a>,
<a class="reference internal" href="#venv.EnvBuilder.create_configuration" title="venv.EnvBuilder.create_configuration"><code class="xref py py-meth docutils literal notranslate"><span class="pre">create_configuration()</span></code></a>, <a class="reference internal" href="#venv.EnvBuilder.setup_python" title="venv.EnvBuilder.setup_python"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setup_python()</span></code></a>,
<a class="reference internal" href="#venv.EnvBuilder.setup_scripts" title="venv.EnvBuilder.setup_scripts"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setup_scripts()</span></code></a> and <a class="reference internal" href="#venv.EnvBuilder.post_setup" title="venv.EnvBuilder.post_setup"><code class="xref py py-meth docutils literal notranslate"><span class="pre">post_setup()</span></code></a> can be overridden.</p>
</dd></dl>
<dl class="method">
<dt id="venv.EnvBuilder.ensure_directories">
<code class="sig-name descname">ensure_directories</code><span class="sig-paren">(</span><em class="sig-param">env_dir</em><span class="sig-paren">)</span><a class="headerlink" href="#venv.EnvBuilder.ensure_directories" title="Permalink to this definition">¶</a></dt>
<dd><p>Creates the environment directory and all necessary directories, and
returns a context object. This is just a holder for attributes (such as
paths), for use by the other methods. The directories are allowed to
exist already, as long as either <code class="docutils literal notranslate"><span class="pre">clear</span></code> or <code class="docutils literal notranslate"><span class="pre">upgrade</span></code> were
specified to allow operating on an existing environment directory.</p>
</dd></dl>
<dl class="method">
<dt id="venv.EnvBuilder.create_configuration">
<code class="sig-name descname">create_configuration</code><span class="sig-paren">(</span><em class="sig-param">context</em><span class="sig-paren">)</span><a class="headerlink" href="#venv.EnvBuilder.create_configuration" title="Permalink to this definition">¶</a></dt>
<dd><p>Creates the <code class="docutils literal notranslate"><span class="pre">pyvenv.cfg</span></code> configuration file in the environment.</p>
</dd></dl>
<dl class="method">
<dt id="venv.EnvBuilder.setup_python">
<code class="sig-name descname">setup_python</code><span class="sig-paren">(</span><em class="sig-param">context</em><span class="sig-paren">)</span><a class="headerlink" href="#venv.EnvBuilder.setup_python" title="Permalink to this definition">¶</a></dt>
<dd><p>Creates a copy or symlink to the Python executable in the environment.
On POSIX systems, if a specific executable <code class="docutils literal notranslate"><span class="pre">python3.x</span></code> was used,
symlinks to <code class="docutils literal notranslate"><span class="pre">python</span></code> and <code class="docutils literal notranslate"><span class="pre">python3</span></code> will be created pointing to that
executable, unless files with those names already exist.</p>
</dd></dl>
<dl class="method">
<dt id="venv.EnvBuilder.setup_scripts">
<code class="sig-name descname">setup_scripts</code><span class="sig-paren">(</span><em class="sig-param">context</em><span class="sig-paren">)</span><a class="headerlink" href="#venv.EnvBuilder.setup_scripts" title="Permalink to this definition">¶</a></dt>
<dd><p>Installs activation scripts appropriate to the platform into the virtual
environment.</p>
</dd></dl>
<dl class="method">
<dt id="venv.EnvBuilder.post_setup">
<code class="sig-name descname">post_setup</code><span class="sig-paren">(</span><em class="sig-param">context</em><span class="sig-paren">)</span><a class="headerlink" href="#venv.EnvBuilder.post_setup" title="Permalink to this definition">¶</a></dt>
<dd><p>A placeholder method which can be overridden in third party
implementations to pre-install packages in the virtual environment or
perform other post-creation steps.</p>
</dd></dl>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7.2: </span>Windows now uses redirector scripts for <code class="docutils literal notranslate"><span class="pre">python[w].exe</span></code> instead of
copying the actual binaries. In 3.7.2 only <a class="reference internal" href="#venv.EnvBuilder.setup_python" title="venv.EnvBuilder.setup_python"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setup_python()</span></code></a> does
nothing unless running from a build in the source tree.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7.3: </span>Windows copies the redirector scripts as part of <a class="reference internal" href="#venv.EnvBuilder.setup_python" title="venv.EnvBuilder.setup_python"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setup_python()</span></code></a>
instead of <a class="reference internal" href="#venv.EnvBuilder.setup_scripts" title="venv.EnvBuilder.setup_scripts"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setup_scripts()</span></code></a>. This was not the case in 3.7.2.
When using symlinks, the original executables will be linked.</p>
</div>
<p>In addition, <a class="reference internal" href="#venv.EnvBuilder" title="venv.EnvBuilder"><code class="xref py py-class docutils literal notranslate"><span class="pre">EnvBuilder</span></code></a> provides this utility method that can be
called from <a class="reference internal" href="#venv.EnvBuilder.setup_scripts" title="venv.EnvBuilder.setup_scripts"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setup_scripts()</span></code></a> or <a class="reference internal" href="#venv.EnvBuilder.post_setup" title="venv.EnvBuilder.post_setup"><code class="xref py py-meth docutils literal notranslate"><span class="pre">post_setup()</span></code></a> in subclasses to
assist in installing custom scripts into the virtual environment.</p>
<dl class="method">
<dt id="venv.EnvBuilder.install_scripts">
<code class="sig-name descname">install_scripts</code><span class="sig-paren">(</span><em class="sig-param">context</em>, <em class="sig-param">path</em><span class="sig-paren">)</span><a class="headerlink" href="#venv.EnvBuilder.install_scripts" title="Permalink to this definition">¶</a></dt>
<dd><p><em>path</em> is the path to a directory that should contain subdirectories
“common”, “posix”, “nt”, each containing scripts destined for the bin
directory in the environment. The contents of “common” and the
directory corresponding to <a class="reference internal" href="os.html#os.name" title="os.name"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.name</span></code></a> are copied after some text
replacement of placeholders:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">__VENV_DIR__</span></code> is replaced with the absolute path of the environment
directory.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">__VENV_NAME__</span></code> is replaced with the environment name (final path
segment of environment directory).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">__VENV_PROMPT__</span></code> is replaced with the prompt (the environment
name surrounded by parentheses and with a following space)</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">__VENV_BIN_NAME__</span></code> is replaced with the name of the bin directory
(either <code class="docutils literal notranslate"><span class="pre">bin</span></code> or <code class="docutils literal notranslate"><span class="pre">Scripts</span></code>).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">__VENV_PYTHON__</span></code> is replaced with the absolute path of the
environment’s executable.</p></li>
</ul>
<p>The directories are allowed to exist (for when an existing environment
is being upgraded).</p>
</dd></dl>
</dd></dl>
<p>There is also a module-level convenience function:</p>
<dl class="function">
<dt id="venv.create">
<code class="sig-prename descclassname">venv.</code><code class="sig-name descname">create</code><span class="sig-paren">(</span><em class="sig-param">env_dir</em>, <em class="sig-param">system_site_packages=False</em>, <em class="sig-param">clear=False</em>, <em class="sig-param">symlinks=False</em>, <em class="sig-param">with_pip=False</em>, <em class="sig-param">prompt=None</em><span class="sig-paren">)</span><a class="headerlink" href="#venv.create" title="Permalink to this definition">¶</a></dt>
<dd><p>Create an <a class="reference internal" href="#venv.EnvBuilder" title="venv.EnvBuilder"><code class="xref py py-class docutils literal notranslate"><span class="pre">EnvBuilder</span></code></a> with the given keyword arguments, and call its
<a class="reference internal" href="#venv.EnvBuilder.create" title="venv.EnvBuilder.create"><code class="xref py py-meth docutils literal notranslate"><span class="pre">create()</span></code></a> method with the <em>env_dir</em> argument.</p>
<div class="versionadded">
<p><span class="versionmodified added">New in version 3.3.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.4: </span>Added the <code class="docutils literal notranslate"><span class="pre">with_pip</span></code> parameter</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.6: </span>Added the <code class="docutils literal notranslate"><span class="pre">prompt</span></code> parameter</p>
</div>
</dd></dl>
</div>
<div class="section" id="an-example-of-extending-envbuilder">
<h2>An example of extending <code class="docutils literal notranslate"><span class="pre">EnvBuilder</span></code><a class="headerlink" href="#an-example-of-extending-envbuilder" title="Permalink to this headline">¶</a></h2>
<p>The following script shows how to extend <a class="reference internal" href="#venv.EnvBuilder" title="venv.EnvBuilder"><code class="xref py py-class docutils literal notranslate"><span class="pre">EnvBuilder</span></code></a> by implementing a
subclass which installs setuptools and pip into a created virtual environment:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">os</span>
<span class="kn">import</span> <span class="nn">os.path</span>
<span class="kn">from</span> <span class="nn">subprocess</span> <span class="kn">import</span> <span class="n">Popen</span><span class="p">,</span> <span class="n">PIPE</span>
<span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">from</span> <span class="nn">threading</span> <span class="kn">import</span> <span class="n">Thread</span>
<span class="kn">from</span> <span class="nn">urllib.parse</span> <span class="kn">import</span> <span class="n">urlparse</span>
<span class="kn">from</span> <span class="nn">urllib.request</span> <span class="kn">import</span> <span class="n">urlretrieve</span>
<span class="kn">import</span> <span class="nn">venv</span>
<span class="k">class</span> <span class="nc">ExtendedEnvBuilder</span><span class="p">(</span><span class="n">venv</span><span class="o">.</span><span class="n">EnvBuilder</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> This builder installs setuptools and pip so that you can pip or</span>
<span class="sd"> easy_install other packages into the created virtual environment.</span>
<span class="sd"> :param nodist: If true, setuptools and pip are not installed into the</span>
<span class="sd"> created virtual environment.</span>
<span class="sd"> :param nopip: If true, pip is not installed into the created</span>
<span class="sd"> virtual environment.</span>
<span class="sd"> :param progress: If setuptools or pip are installed, the progress of the</span>
<span class="sd"> installation can be monitored by passing a progress</span>
<span class="sd"> callable. If specified, it is called with two</span>
<span class="sd"> arguments: a string indicating some progress, and a</span>
<span class="sd"> context indicating where the string is coming from.</span>
<span class="sd"> The context argument can have one of three values:</span>
<span class="sd"> 'main', indicating that it is called from virtualize()</span>
<span class="sd"> itself, and 'stdout' and 'stderr', which are obtained</span>
<span class="sd"> by reading lines from the output streams of a subprocess</span>
<span class="sd"> which is used to install the app.</span>
<span class="sd"> If a callable is not specified, default progress</span>
<span class="sd"> information is output to sys.stderr.</span>
<span class="sd"> """</span>
<span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">nodist</span> <span class="o">=</span> <span class="n">kwargs</span><span class="o">.</span><span class="n">pop</span><span class="p">(</span><span class="s1">'nodist'</span><span class="p">,</span> <span class="kc">False</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">nopip</span> <span class="o">=</span> <span class="n">kwargs</span><span class="o">.</span><span class="n">pop</span><span class="p">(</span><span class="s1">'nopip'</span><span class="p">,</span> <span class="kc">False</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">progress</span> <span class="o">=</span> <span class="n">kwargs</span><span class="o">.</span><span class="n">pop</span><span class="p">(</span><span class="s1">'progress'</span><span class="p">,</span> <span class="kc">None</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">verbose</span> <span class="o">=</span> <span class="n">kwargs</span><span class="o">.</span><span class="n">pop</span><span class="p">(</span><span class="s1">'verbose'</span><span class="p">,</span> <span class="kc">False</span><span class="p">)</span>
<span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">post_setup</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">context</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Set up any packages which need to be pre-installed into the</span>
<span class="sd"> virtual environment being created.</span>
<span class="sd"> :param context: The information for the virtual environment</span>
<span class="sd"> creation request being processed.</span>
<span class="sd"> """</span>
<span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="p">[</span><span class="s1">'VIRTUAL_ENV'</span><span class="p">]</span> <span class="o">=</span> <span class="n">context</span><span class="o">.</span><span class="n">env_dir</span>
<span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">nodist</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">install_setuptools</span><span class="p">(</span><span class="n">context</span><span class="p">)</span>
<span class="c1"># Can't install pip without setuptools</span>
<span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">nopip</span> <span class="ow">and</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">nodist</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">install_pip</span><span class="p">(</span><span class="n">context</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">reader</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">stream</span><span class="p">,</span> <span class="n">context</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Read lines from a subprocess' output stream and either pass to a progress</span>
<span class="sd"> callable (if specified) or write progress information to sys.stderr.</span>
<span class="sd"> """</span>
<span class="n">progress</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">progress</span>
<span class="k">while</span> <span class="kc">True</span><span class="p">:</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">stream</span><span class="o">.</span><span class="n">readline</span><span class="p">()</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">s</span><span class="p">:</span>
<span class="k">break</span>
<span class="k">if</span> <span class="n">progress</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">progress</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="n">context</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">verbose</span><span class="p">:</span>
<span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'.'</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">s</span><span class="o">.</span><span class="n">decode</span><span class="p">(</span><span class="s1">'utf-8'</span><span class="p">))</span>
<span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>
<span class="n">stream</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="k">def</span> <span class="nf">install_script</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">context</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">url</span><span class="p">):</span>
<span class="n">_</span><span class="p">,</span> <span class="n">_</span><span class="p">,</span> <span class="n">path</span><span class="p">,</span> <span class="n">_</span><span class="p">,</span> <span class="n">_</span><span class="p">,</span> <span class="n">_</span> <span class="o">=</span> <span class="n">urlparse</span><span class="p">(</span><span class="n">url</span><span class="p">)</span>
<span class="n">fn</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">path</span><span class="p">)[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span>
<span class="n">binpath</span> <span class="o">=</span> <span class="n">context</span><span class="o">.</span><span class="n">bin_path</span>
<span class="n">distpath</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">binpath</span><span class="p">,</span> <span class="n">fn</span><span class="p">)</span>
<span class="c1"># Download script into the virtual environment's binaries folder</span>
<span class="n">urlretrieve</span><span class="p">(</span><span class="n">url</span><span class="p">,</span> <span class="n">distpath</span><span class="p">)</span>
<span class="n">progress</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">progress</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">verbose</span><span class="p">:</span>
<span class="n">term</span> <span class="o">=</span> <span class="s1">'</span><span class="se">\n</span><span class="s1">'</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">term</span> <span class="o">=</span> <span class="s1">''</span>
<span class="k">if</span> <span class="n">progress</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">progress</span><span class="p">(</span><span class="s1">'Installing </span><span class="si">%s</span><span class="s1"> ...</span><span class="si">%s</span><span class="s1">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="n">term</span><span class="p">),</span> <span class="s1">'main'</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'Installing </span><span class="si">%s</span><span class="s1"> ...</span><span class="si">%s</span><span class="s1">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="n">term</span><span class="p">))</span>
<span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>
<span class="c1"># Install in the virtual environment</span>
<span class="n">args</span> <span class="o">=</span> <span class="p">[</span><span class="n">context</span><span class="o">.</span><span class="n">env_exe</span><span class="p">,</span> <span class="n">fn</span><span class="p">]</span>
<span class="n">p</span> <span class="o">=</span> <span class="n">Popen</span><span class="p">(</span><span class="n">args</span><span class="p">,</span> <span class="n">stdout</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">stderr</span><span class="o">=</span><span class="n">PIPE</span><span class="p">,</span> <span class="n">cwd</span><span class="o">=</span><span class="n">binpath</span><span class="p">)</span>
<span class="n">t1</span> <span class="o">=</span> <span class="n">Thread</span><span class="p">(</span><span class="n">target</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">reader</span><span class="p">,</span> <span class="n">args</span><span class="o">=</span><span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">stdout</span><span class="p">,</span> <span class="s1">'stdout'</span><span class="p">))</span>
<span class="n">t1</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
<span class="n">t2</span> <span class="o">=</span> <span class="n">Thread</span><span class="p">(</span><span class="n">target</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">reader</span><span class="p">,</span> <span class="n">args</span><span class="o">=</span><span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">stderr</span><span class="p">,</span> <span class="s1">'stderr'</span><span class="p">))</span>
<span class="n">t2</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
<span class="n">p</span><span class="o">.</span><span class="n">wait</span><span class="p">()</span>
<span class="n">t1</span><span class="o">.</span><span class="n">join</span><span class="p">()</span>
<span class="n">t2</span><span class="o">.</span><span class="n">join</span><span class="p">()</span>
<span class="k">if</span> <span class="n">progress</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">progress</span><span class="p">(</span><span class="s1">'done.'</span><span class="p">,</span> <span class="s1">'main'</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'done.</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="c1"># Clean up - no longer needed</span>
<span class="n">os</span><span class="o">.</span><span class="n">unlink</span><span class="p">(</span><span class="n">distpath</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">install_setuptools</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">context</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Install setuptools in the virtual environment.</span>
<span class="sd"> :param context: The information for the virtual environment</span>
<span class="sd"> creation request being processed.</span>
<span class="sd"> """</span>
<span class="n">url</span> <span class="o">=</span> <span class="s1">'https://bitbucket.org/pypa/setuptools/downloads/ez_setup.py'</span>
<span class="bp">self</span><span class="o">.</span><span class="n">install_script</span><span class="p">(</span><span class="n">context</span><span class="p">,</span> <span class="s1">'setuptools'</span><span class="p">,</span> <span class="n">url</span><span class="p">)</span>
<span class="c1"># clear up the setuptools archive which gets downloaded</span>
<span class="n">pred</span> <span class="o">=</span> <span class="k">lambda</span> <span class="n">o</span><span class="p">:</span> <span class="n">o</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="s1">'setuptools-'</span><span class="p">)</span> <span class="ow">and</span> <span class="n">o</span><span class="o">.</span><span class="n">endswith</span><span class="p">(</span><span class="s1">'.tar.gz'</span><span class="p">)</span>
<span class="n">files</span> <span class="o">=</span> <span class="nb">filter</span><span class="p">(</span><span class="n">pred</span><span class="p">,</span> <span class="n">os</span><span class="o">.</span><span class="n">listdir</span><span class="p">(</span><span class="n">context</span><span class="o">.</span><span class="n">bin_path</span><span class="p">))</span>
<span class="k">for</span> <span class="n">f</span> <span class="ow">in</span> <span class="n">files</span><span class="p">:</span>
<span class="n">f</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">context</span><span class="o">.</span><span class="n">bin_path</span><span class="p">,</span> <span class="n">f</span><span class="p">)</span>
<span class="n">os</span><span class="o">.</span><span class="n">unlink</span><span class="p">(</span><span class="n">f</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">install_pip</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">context</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Install pip in the virtual environment.</span>
<span class="sd"> :param context: The information for the virtual environment</span>
<span class="sd"> creation request being processed.</span>
<span class="sd"> """</span>
<span class="n">url</span> <span class="o">=</span> <span class="s1">'https://raw.github.com/pypa/pip/master/contrib/get-pip.py'</span>
<span class="bp">self</span><span class="o">.</span><span class="n">install_script</span><span class="p">(</span><span class="n">context</span><span class="p">,</span> <span class="s1">'pip'</span><span class="p">,</span> <span class="n">url</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">main</span><span class="p">(</span><span class="n">args</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
<span class="n">compatible</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">if</span> <span class="n">sys</span><span class="o">.</span><span class="n">version_info</span> <span class="o"><</span> <span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">):</span>
<span class="n">compatible</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">elif</span> <span class="ow">not</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">sys</span><span class="p">,</span> <span class="s1">'base_prefix'</span><span class="p">):</span>
<span class="n">compatible</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">compatible</span><span class="p">:</span>
<span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><span class="s1">'This script is only for use with '</span>
<span class="s1">'Python 3.3 or later'</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="kn">import</span> <span class="nn">argparse</span>
<span class="n">parser</span> <span class="o">=</span> <span class="n">argparse</span><span class="o">.</span><span class="n">ArgumentParser</span><span class="p">(</span><span class="n">prog</span><span class="o">=</span><span class="vm">__name__</span><span class="p">,</span>
<span class="n">description</span><span class="o">=</span><span class="s1">'Creates virtual Python '</span>
<span class="s1">'environments in one or '</span>
<span class="s1">'more target '</span>
<span class="s1">'directories.'</span><span class="p">)</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">'dirs'</span><span class="p">,</span> <span class="n">metavar</span><span class="o">=</span><span class="s1">'ENV_DIR'</span><span class="p">,</span> <span class="n">nargs</span><span class="o">=</span><span class="s1">'+'</span><span class="p">,</span>
<span class="n">help</span><span class="o">=</span><span class="s1">'A directory in which to create the</span>
<span class="s1">'virtual environment.'</span><span class="p">)</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">'--no-setuptools'</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
<span class="n">action</span><span class="o">=</span><span class="s1">'store_true'</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">'nodist'</span><span class="p">,</span>
<span class="n">help</span><span class="o">=</span><span class="s2">"Don't install setuptools or pip in the "</span>
<span class="s2">"virtual environment."</span><span class="p">)</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">'--no-pip'</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
<span class="n">action</span><span class="o">=</span><span class="s1">'store_true'</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">'nopip'</span><span class="p">,</span>
<span class="n">help</span><span class="o">=</span><span class="s2">"Don't install pip in the virtual "</span>
<span class="s2">"environment."</span><span class="p">)</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">'--system-site-packages'</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
<span class="n">action</span><span class="o">=</span><span class="s1">'store_true'</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">'system_site'</span><span class="p">,</span>
<span class="n">help</span><span class="o">=</span><span class="s1">'Give the virtual environment access to the '</span>
<span class="s1">'system site-packages dir.'</span><span class="p">)</span>
<span class="k">if</span> <span class="n">os</span><span class="o">.</span><span class="n">name</span> <span class="o">==</span> <span class="s1">'nt'</span><span class="p">:</span>
<span class="n">use_symlinks</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">use_symlinks</span> <span class="o">=</span> <span class="kc">True</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">'--symlinks'</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="n">use_symlinks</span><span class="p">,</span>
<span class="n">action</span><span class="o">=</span><span class="s1">'store_true'</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">'symlinks'</span><span class="p">,</span>
<span class="n">help</span><span class="o">=</span><span class="s1">'Try to use symlinks rather than copies, '</span>
<span class="s1">'when symlinks are not the default for '</span>
<span class="s1">'the platform.'</span><span class="p">)</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">'--clear'</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s1">'store_true'</span><span class="p">,</span>
<span class="n">dest</span><span class="o">=</span><span class="s1">'clear'</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s1">'Delete the contents of the '</span>
<span class="s1">'virtual environment '</span>
<span class="s1">'directory if it already '</span>
<span class="s1">'exists, before virtual '</span>
<span class="s1">'environment creation.'</span><span class="p">)</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">'--upgrade'</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s1">'store_true'</span><span class="p">,</span>
<span class="n">dest</span><span class="o">=</span><span class="s1">'upgrade'</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s1">'Upgrade the virtual '</span>
<span class="s1">'environment directory to '</span>
<span class="s1">'use this version of '</span>
<span class="s1">'Python, assuming Python '</span>
<span class="s1">'has been upgraded '</span>
<span class="s1">'in-place.'</span><span class="p">)</span>
<span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">'--verbose'</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s1">'store_true'</span><span class="p">,</span>
<span class="n">dest</span><span class="o">=</span><span class="s1">'verbose'</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s1">'Display the output '</span>
<span class="s1">'from the scripts which '</span>
<span class="s1">'install setuptools and pip.'</span><span class="p">)</span>
<span class="n">options</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">(</span><span class="n">args</span><span class="p">)</span>
<span class="k">if</span> <span class="n">options</span><span class="o">.</span><span class="n">upgrade</span> <span class="ow">and</span> <span class="n">options</span><span class="o">.</span><span class="n">clear</span><span class="p">:</span>
<span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><span class="s1">'you cannot supply --upgrade and --clear together.'</span><span class="p">)</span>
<span class="n">builder</span> <span class="o">=</span> <span class="n">ExtendedEnvBuilder</span><span class="p">(</span><span class="n">system_site_packages</span><span class="o">=</span><span class="n">options</span><span class="o">.</span><span class="n">system_site</span><span class="p">,</span>
<span class="n">clear</span><span class="o">=</span><span class="n">options</span><span class="o">.</span><span class="n">clear</span><span class="p">,</span>
<span class="n">symlinks</span><span class="o">=</span><span class="n">options</span><span class="o">.</span><span class="n">symlinks</span><span class="p">,</span>
<span class="n">upgrade</span><span class="o">=</span><span class="n">options</span><span class="o">.</span><span class="n">upgrade</span><span class="p">,</span>
<span class="n">nodist</span><span class="o">=</span><span class="n">options</span><span class="o">.</span><span class="n">nodist</span><span class="p">,</span>
<span class="n">nopip</span><span class="o">=</span><span class="n">options</span><span class="o">.</span><span class="n">nopip</span><span class="p">,</span>
<span class="n">verbose</span><span class="o">=</span><span class="n">options</span><span class="o">.</span><span class="n">verbose</span><span class="p">)</span>
<span class="k">for</span> <span class="n">d</span> <span class="ow">in</span> <span class="n">options</span><span class="o">.</span><span class="n">dirs</span><span class="p">:</span>
<span class="n">builder</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">d</span><span class="p">)</span>
<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s1">'__main__'</span><span class="p">:</span>
<span class="n">rc</span> <span class="o">=</span> <span class="mi">1</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">main</span><span class="p">()</span>
<span class="n">rc</span> <span class="o">=</span> <span class="mi">0</span>
<span class="k">except</span> <span class="ne">Exception</span> <span class="k">as</span> <span class="n">e</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">'Error: </span><span class="si">%s</span><span class="s1">'</span> <span class="o">%</span> <span class="n">e</span><span class="p">,</span> <span class="n">file</span><span class="o">=</span><span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="p">)</span>
<span class="n">sys</span><span class="o">.</span><span class="n">exit</span><span class="p">(</span><span class="n">rc</span><span class="p">)</span>
</pre></div>
</div>
<p>This script is also available for download <a class="reference external" href="https://gist.github.com/vsajip/4673395">online</a>.</p>
</div>
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<ul>
<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">venv</span></code> — Creation of virtual environments</a><ul>
<li><a class="reference internal" href="#creating-virtual-environments">Creating virtual environments</a></li>
<li><a class="reference internal" href="#api">API</a></li>
<li><a class="reference internal" href="#an-example-of-extending-envbuilder">An example of extending <code class="docutils literal notranslate"><span class="pre">EnvBuilder</span></code></a></li>
</ul>
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<h4>Previous topic</h4>
<p class="topless"><a href="ensurepip.html"
title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">ensurepip</span></code> — Bootstrapping the <code class="docutils literal notranslate"><span class="pre">pip</span></code> installer</a></p>
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title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">zipapp</span></code> — Manage executable Python zip archives</a></p>
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