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<div class="section" id="module-pdb">
<span id="pdb-the-python-debugger"></span><span id="debugger"></span><h1>26.2. <a class="reference internal" href="#module-pdb" title="pdb: The Python debugger for interactive interpreters."><tt class="xref py py-mod docutils literal"><span class="pre">pdb</span></tt></a> — The Python Debugger<a class="headerlink" href="#module-pdb" title="Permalink to this headline">¶</a></h1>
<p id="index-0">The module <a class="reference internal" href="#module-pdb" title="pdb: The Python debugger for interactive interpreters."><tt class="xref py py-mod docutils literal"><span class="pre">pdb</span></tt></a> defines an interactive source code debugger for Python
programs. It supports setting (conditional) breakpoints and single stepping at
the source line level, inspection of stack frames, source code listing, and
evaluation of arbitrary Python code in the context of any stack frame. It also
supports post-mortem debugging and can be called under program control.</p>
<p id="index-1">The debugger is extensible – it is actually defined as the class <a class="reference internal" href="#pdb.Pdb" title="pdb.Pdb"><tt class="xref py py-class docutils literal"><span class="pre">Pdb</span></tt></a>.
This is currently undocumented but easily understood by reading the source. The
extension interface uses the modules <a class="reference internal" href="bdb.html#module-bdb" title="bdb: Debugger framework."><tt class="xref py py-mod docutils literal"><span class="pre">bdb</span></tt></a> and <a class="reference internal" href="cmd.html#module-cmd" title="cmd: Build line-oriented command interpreters."><tt class="xref py py-mod docutils literal"><span class="pre">cmd</span></tt></a>.</p>
<p>The debugger’s prompt is <tt class="docutils literal"><span class="pre">(Pdb)</span></tt>. Typical usage to run a program under control
of the debugger is:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">pdb</span>
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">mymodule</span>
<span class="gp">>>> </span><span class="n">pdb</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="s">'mymodule.test()'</span><span class="p">)</span>
<span class="go">> <string>(0)?()</span>
<span class="go">(Pdb) continue</span>
<span class="go">> <string>(1)?()</span>
<span class="go">(Pdb) continue</span>
<span class="go">NameError: 'spam'</span>
<span class="go">> <string>(1)?()</span>
<span class="go">(Pdb)</span>
</pre></div>
</div>
<p><tt class="file docutils literal"><span class="pre">pdb.py</span></tt> can also be invoked as a script to debug other scripts. For
example:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="n">python3</span> <span class="o">-</span><span class="n">m</span> <span class="n">pdb</span> <span class="n">myscript</span><span class="o">.</span><span class="n">py</span>
</pre></div>
</div>
<p>When invoked as a script, pdb will automatically enter post-mortem debugging if
the program being debugged exits abnormally. After post-mortem debugging (or
after normal exit of the program), pdb will restart the program. Automatic
restarting preserves pdb’s state (such as breakpoints) and in most cases is more
useful than quitting the debugger upon program’s exit.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.2: </span><tt class="file docutils literal"><span class="pre">pdb.py</span></tt> now accepts a <tt class="docutils literal"><span class="pre">-c</span></tt> option that executes commands as if given
in a <tt class="file docutils literal"><span class="pre">.pdbrc</span></tt> file, see <a class="reference internal" href="#debugger-commands"><em>Debugger Commands</em></a>.</p>
<p>The typical usage to break into the debugger from a running program is to
insert</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">pdb</span><span class="p">;</span> <span class="n">pdb</span><span class="o">.</span><span class="n">set_trace</span><span class="p">()</span>
</pre></div>
</div>
<p>at the location you want to break into the debugger. You can then step through
the code following this statement, and continue running without the debugger
using the <a class="reference internal" href="#pdbcommand-continue"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">continue</span></tt></a> command.</p>
<p>The typical usage to inspect a crashed program is:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">pdb</span>
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">mymodule</span>
<span class="gp">>>> </span><span class="n">mymodule</span><span class="o">.</span><span class="n">test</span><span class="p">()</span>
<span class="gt">Traceback (most recent call last):</span>
File <span class="nb">"<stdin>"</span>, line <span class="m">1</span>, in <span class="n-Identifier">?</span>
File <span class="nb">"./mymodule.py"</span>, line <span class="m">4</span>, in <span class="n-Identifier">test</span>
<span class="n">test2</span><span class="p">()</span>
File <span class="nb">"./mymodule.py"</span>, line <span class="m">3</span>, in <span class="n-Identifier">test2</span>
<span class="nb">print</span><span class="p">(</span><span class="n">spam</span><span class="p">)</span>
<span class="nc">NameError</span>: <span class="n-Identifier">spam</span>
<span class="gp">>>> </span><span class="n">pdb</span><span class="o">.</span><span class="n">pm</span><span class="p">()</span>
<span class="go">> ./mymodule.py(3)test2()</span>
<span class="go">-> print(spam)</span>
<span class="go">(Pdb)</span>
</pre></div>
</div>
<p>The module defines the following functions; each enters the debugger in a
slightly different way:</p>
<dl class="function">
<dt id="pdb.run">
<tt class="descclassname">pdb.</tt><tt class="descname">run</tt><big>(</big><em>statement</em>, <em>globals=None</em>, <em>locals=None</em><big>)</big><a class="headerlink" href="#pdb.run" title="Permalink to this definition">¶</a></dt>
<dd><p>Execute the <em>statement</em> (given as a string or a code object) under debugger
control. The debugger prompt appears before any code is executed; you can
set breakpoints and type <a class="reference internal" href="#pdbcommand-continue"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">continue</span></tt></a>, or you can step through the
statement using <a class="reference internal" href="#pdbcommand-step"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">step</span></tt></a> or <a class="reference internal" href="#pdbcommand-next"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">next</span></tt></a> (all these commands are
explained below). The optional <em>globals</em> and <em>locals</em> arguments specify the
environment in which the code is executed; by default the dictionary of the
module <a class="reference internal" href="__main__.html#module-__main__" title="__main__: The environment where the top-level script is run."><tt class="xref py py-mod docutils literal"><span class="pre">__main__</span></tt></a> is used. (See the explanation of the built-in
<a class="reference internal" href="functions.html#exec" title="exec"><tt class="xref py py-func docutils literal"><span class="pre">exec()</span></tt></a> or <a class="reference internal" href="functions.html#eval" title="eval"><tt class="xref py py-func docutils literal"><span class="pre">eval()</span></tt></a> functions.)</p>
</dd></dl>
<dl class="function">
<dt id="pdb.runeval">
<tt class="descclassname">pdb.</tt><tt class="descname">runeval</tt><big>(</big><em>expression</em>, <em>globals=None</em>, <em>locals=None</em><big>)</big><a class="headerlink" href="#pdb.runeval" title="Permalink to this definition">¶</a></dt>
<dd><p>Evaluate the <em>expression</em> (given as a string or a code object) under debugger
control. When <a class="reference internal" href="#pdb.runeval" title="pdb.runeval"><tt class="xref py py-func docutils literal"><span class="pre">runeval()</span></tt></a> returns, it returns the value of the
expression. Otherwise this function is similar to <a class="reference internal" href="#pdb.run" title="pdb.run"><tt class="xref py py-func docutils literal"><span class="pre">run()</span></tt></a>.</p>
</dd></dl>
<dl class="function">
<dt id="pdb.runcall">
<tt class="descclassname">pdb.</tt><tt class="descname">runcall</tt><big>(</big><em>function</em>, <em>*args</em>, <em>**kwds</em><big>)</big><a class="headerlink" href="#pdb.runcall" title="Permalink to this definition">¶</a></dt>
<dd><p>Call the <em>function</em> (a function or method object, not a string) with the
given arguments. When <a class="reference internal" href="#pdb.runcall" title="pdb.runcall"><tt class="xref py py-func docutils literal"><span class="pre">runcall()</span></tt></a> returns, it returns whatever the
function call returned. The debugger prompt appears as soon as the function
is entered.</p>
</dd></dl>
<dl class="function">
<dt id="pdb.set_trace">
<tt class="descclassname">pdb.</tt><tt class="descname">set_trace</tt><big>(</big><big>)</big><a class="headerlink" href="#pdb.set_trace" title="Permalink to this definition">¶</a></dt>
<dd><p>Enter the debugger at the calling stack frame. This is useful to hard-code a
breakpoint at a given point in a program, even if the code is not otherwise
being debugged (e.g. when an assertion fails).</p>
</dd></dl>
<dl class="function">
<dt id="pdb.post_mortem">
<tt class="descclassname">pdb.</tt><tt class="descname">post_mortem</tt><big>(</big><em>traceback=None</em><big>)</big><a class="headerlink" href="#pdb.post_mortem" title="Permalink to this definition">¶</a></dt>
<dd><p>Enter post-mortem debugging of the given <em>traceback</em> object. If no
<em>traceback</em> is given, it uses the one of the exception that is currently
being handled (an exception must be being handled if the default is to be
used).</p>
</dd></dl>
<dl class="function">
<dt id="pdb.pm">
<tt class="descclassname">pdb.</tt><tt class="descname">pm</tt><big>(</big><big>)</big><a class="headerlink" href="#pdb.pm" title="Permalink to this definition">¶</a></dt>
<dd><p>Enter post-mortem debugging of the traceback found in
<a class="reference internal" href="sys.html#sys.last_traceback" title="sys.last_traceback"><tt class="xref py py-data docutils literal"><span class="pre">sys.last_traceback</span></tt></a>.</p>
</dd></dl>
<p>The <tt class="docutils literal"><span class="pre">run*</span></tt> functions and <a class="reference internal" href="#pdb.set_trace" title="pdb.set_trace"><tt class="xref py py-func docutils literal"><span class="pre">set_trace()</span></tt></a> are aliases for instantiating the
<a class="reference internal" href="#pdb.Pdb" title="pdb.Pdb"><tt class="xref py py-class docutils literal"><span class="pre">Pdb</span></tt></a> class and calling the method of the same name. If you want to
access further features, you have to do this yourself:</p>
<dl class="class">
<dt id="pdb.Pdb">
<em class="property">class </em><tt class="descclassname">pdb.</tt><tt class="descname">Pdb</tt><big>(</big><em>completekey='tab'</em>, <em>stdin=None</em>, <em>stdout=None</em>, <em>skip=None</em>, <em>nosigint=False</em><big>)</big><a class="headerlink" href="#pdb.Pdb" title="Permalink to this definition">¶</a></dt>
<dd><p><a class="reference internal" href="#pdb.Pdb" title="pdb.Pdb"><tt class="xref py py-class docutils literal"><span class="pre">Pdb</span></tt></a> is the debugger class.</p>
<p>The <em>completekey</em>, <em>stdin</em> and <em>stdout</em> arguments are passed to the
underlying <a class="reference internal" href="cmd.html#cmd.Cmd" title="cmd.Cmd"><tt class="xref py py-class docutils literal"><span class="pre">cmd.Cmd</span></tt></a> class; see the description there.</p>
<p>The <em>skip</em> argument, if given, must be an iterable of glob-style module name
patterns. The debugger will not step into frames that originate in a module
that matches one of these patterns. <a class="footnote-reference" href="#id3" id="id1">[1]</a></p>
<p>By default, Pdb sets a handler for the SIGINT signal (which is sent when the
user presses Ctrl-C on the console) when you give a <tt class="docutils literal"><span class="pre">continue</span></tt> command.
This allows you to break into the debugger again by pressing Ctrl-C. If you
want Pdb not to touch the SIGINT handler, set <em>nosigint</em> tot true.</p>
<p>Example call to enable tracing with <em>skip</em>:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">pdb</span><span class="p">;</span> <span class="n">pdb</span><span class="o">.</span><span class="n">Pdb</span><span class="p">(</span><span class="n">skip</span><span class="o">=</span><span class="p">[</span><span class="s">'django.*'</span><span class="p">])</span><span class="o">.</span><span class="n">set_trace</span><span class="p">()</span>
</pre></div>
</div>
<p class="versionadded">
<span class="versionmodified">New in version 3.1: </span>The <em>skip</em> argument.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.2: </span>The <em>nosigint</em> argument. Previously, a SIGINT handler was never set by
Pdb.</p>
<dl class="method">
<dt id="pdb.Pdb.run">
<tt class="descname">run</tt><big>(</big><em>statement</em>, <em>globals=None</em>, <em>locals=None</em><big>)</big><a class="headerlink" href="#pdb.Pdb.run" title="Permalink to this definition">¶</a></dt>
<dt id="pdb.Pdb.runeval">
<tt class="descname">runeval</tt><big>(</big><em>expression</em>, <em>globals=None</em>, <em>locals=None</em><big>)</big><a class="headerlink" href="#pdb.Pdb.runeval" title="Permalink to this definition">¶</a></dt>
<dt id="pdb.Pdb.runcall">
<tt class="descname">runcall</tt><big>(</big><em>function</em>, <em>*args</em>, <em>**kwds</em><big>)</big><a class="headerlink" href="#pdb.Pdb.runcall" title="Permalink to this definition">¶</a></dt>
<dt id="pdb.Pdb.set_trace">
<tt class="descname">set_trace</tt><big>(</big><big>)</big><a class="headerlink" href="#pdb.Pdb.set_trace" title="Permalink to this definition">¶</a></dt>
<dd><p>See the documentation for the functions explained above.</p>
</dd></dl>
</dd></dl>
<div class="section" id="debugger-commands">
<span id="id2"></span><h2>26.2.1. Debugger Commands<a class="headerlink" href="#debugger-commands" title="Permalink to this headline">¶</a></h2>
<p>The commands recognized by the debugger are listed below. Most commands can be
abbreviated to one or two letters as indicated; e.g. <tt class="docutils literal"><span class="pre">h(elp)</span></tt> means that
either <tt class="docutils literal"><span class="pre">h</span></tt> or <tt class="docutils literal"><span class="pre">help</span></tt> can be used to enter the help command (but not <tt class="docutils literal"><span class="pre">he</span></tt>
or <tt class="docutils literal"><span class="pre">hel</span></tt>, nor <tt class="docutils literal"><span class="pre">H</span></tt> or <tt class="docutils literal"><span class="pre">Help</span></tt> or <tt class="docutils literal"><span class="pre">HELP</span></tt>). Arguments to commands must be
separated by whitespace (spaces or tabs). Optional arguments are enclosed in
square brackets (<tt class="docutils literal"><span class="pre">[]</span></tt>) in the command syntax; the square brackets must not be
typed. Alternatives in the command syntax are separated by a vertical bar
(<tt class="docutils literal"><span class="pre">|</span></tt>).</p>
<p>Entering a blank line repeats the last command entered. Exception: if the last
command was a <a class="reference internal" href="#pdbcommand-list"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">list</span></tt></a> command, the next 11 lines are listed.</p>
<p>Commands that the debugger doesn’t recognize are assumed to be Python statements
and are executed in the context of the program being debugged. Python
statements can also be prefixed with an exclamation point (<tt class="docutils literal"><span class="pre">!</span></tt>). This is a
powerful way to inspect the program being debugged; it is even possible to
change a variable or call a function. When an exception occurs in such a
statement, the exception name is printed but the debugger’s state is not
changed.</p>
<p>The debugger supports <a class="reference internal" href="#debugger-aliases"><em>aliases</em></a>. Aliases can have
parameters which allows one a certain level of adaptability to the context under
examination.</p>
<p>Multiple commands may be entered on a single line, separated by <tt class="docutils literal"><span class="pre">;;</span></tt>. (A
single <tt class="docutils literal"><span class="pre">;</span></tt> is not used as it is the separator for multiple commands in a line
that is passed to the Python parser.) No intelligence is applied to separating
the commands; the input is split at the first <tt class="docutils literal"><span class="pre">;;</span></tt> pair, even if it is in the
middle of a quoted string.</p>
<p id="index-2">If a file <tt class="file docutils literal"><span class="pre">.pdbrc</span></tt> exists in the user’s home directory or in the current
directory, it is read in and executed as if it had been typed at the debugger
prompt. This is particularly useful for aliases. If both files exist, the one
in the home directory is read first and aliases defined there can be overridden
by the local file.</p>
<p class="versionchanged">
<span class="versionmodified">Changed in version 3.2: </span><tt class="file docutils literal"><span class="pre">.pdbrc</span></tt> can now contain commands that continue debugging, such as
<a class="reference internal" href="#pdbcommand-continue"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">continue</span></tt></a> or <a class="reference internal" href="#pdbcommand-next"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">next</span></tt></a>. Previously, these commands had no
effect.</p>
<dl class="pdbcommand">
<dt id="pdbcommand-help">
<tt class="descname">h(elp)</tt><tt class="descclassname"> [command]</tt><a class="headerlink" href="#pdbcommand-help" title="Permalink to this definition">¶</a></dt>
<dd><p>Without argument, print the list of available commands. With a <em>command</em> as
argument, print help about that command. <tt class="docutils literal"><span class="pre">help</span> <span class="pre">pdb</span></tt> displays the full
documentation (the docstring of the <a class="reference internal" href="#module-pdb" title="pdb: The Python debugger for interactive interpreters."><tt class="xref py py-mod docutils literal"><span class="pre">pdb</span></tt></a> module). Since the <em>command</em>
argument must be an identifier, <tt class="docutils literal"><span class="pre">help</span> <span class="pre">exec</span></tt> must be entered to get help on
the <tt class="docutils literal"><span class="pre">!</span></tt> command.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-where">
<tt class="descname">w(here)</tt><a class="headerlink" href="#pdbcommand-where" title="Permalink to this definition">¶</a></dt>
<dd><p>Print a stack trace, with the most recent frame at the bottom. An arrow
indicates the current frame, which determines the context of most commands.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-down">
<tt class="descname">d(own)</tt><tt class="descclassname"> [count]</tt><a class="headerlink" href="#pdbcommand-down" title="Permalink to this definition">¶</a></dt>
<dd><p>Move the current frame <em>count</em> (default one) levels down in the stack trace
(to a newer frame).</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-up">
<tt class="descname">u(p)</tt><tt class="descclassname"> [count]</tt><a class="headerlink" href="#pdbcommand-up" title="Permalink to this definition">¶</a></dt>
<dd><p>Move the current frame <em>count</em> (default one) levels up in the stack trace (to
an older frame).</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-break">
<tt class="descname">b(reak)</tt><tt class="descclassname"> [([filename:]lineno | function) [, condition]]</tt><a class="headerlink" href="#pdbcommand-break" title="Permalink to this definition">¶</a></dt>
<dd><p>With a <em>lineno</em> argument, set a break there in the current file. With a
<em>function</em> argument, set a break at the first executable statement within
that function. The line number may be prefixed with a filename and a colon,
to specify a breakpoint in another file (probably one that hasn’t been loaded
yet). The file is searched on <a class="reference internal" href="sys.html#sys.path" title="sys.path"><tt class="xref py py-data docutils literal"><span class="pre">sys.path</span></tt></a>. Note that each breakpoint
is assigned a number to which all the other breakpoint commands refer.</p>
<p>If a second argument is present, it is an expression which must evaluate to
true before the breakpoint is honored.</p>
<p>Without argument, list all breaks, including for each breakpoint, the number
of times that breakpoint has been hit, the current ignore count, and the
associated condition if any.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-tbreak">
<tt class="descname">tbreak</tt><tt class="descclassname"> [([filename:]lineno | function) [, condition]]</tt><a class="headerlink" href="#pdbcommand-tbreak" title="Permalink to this definition">¶</a></dt>
<dd><p>Temporary breakpoint, which is removed automatically when it is first hit.
The arguments are the same as for <a class="reference internal" href="#pdbcommand-break"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">break</span></tt></a>.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-clear">
<tt class="descname">cl(ear)</tt><tt class="descclassname"> [filename:lineno | bpnumber [bpnumber ...]]</tt><a class="headerlink" href="#pdbcommand-clear" title="Permalink to this definition">¶</a></dt>
<dd><p>With a <em>filename:lineno</em> argument, clear all the breakpoints at this line.
With a space separated list of breakpoint numbers, clear those breakpoints.
Without argument, clear all breaks (but first ask confirmation).</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-disable">
<tt class="descname">disable</tt><tt class="descclassname"> [bpnumber [bpnumber ...]]</tt><a class="headerlink" href="#pdbcommand-disable" title="Permalink to this definition">¶</a></dt>
<dd><p>Disable the breakpoints given as a space separated list of breakpoint
numbers. Disabling a breakpoint means it cannot cause the program to stop
execution, but unlike clearing a breakpoint, it remains in the list of
breakpoints and can be (re-)enabled.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-enable">
<tt class="descname">enable</tt><tt class="descclassname"> [bpnumber [bpnumber ...]]</tt><a class="headerlink" href="#pdbcommand-enable" title="Permalink to this definition">¶</a></dt>
<dd><p>Enable the breakpoints specified.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-ignore">
<tt class="descname">ignore</tt><tt class="descclassname"> bpnumber [count]</tt><a class="headerlink" href="#pdbcommand-ignore" title="Permalink to this definition">¶</a></dt>
<dd><p>Set the ignore count for the given breakpoint number. If count is omitted,
the ignore count is set to 0. A breakpoint becomes active when the ignore
count is zero. When non-zero, the count is decremented each time the
breakpoint is reached and the breakpoint is not disabled and any associated
condition evaluates to true.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-condition">
<tt class="descname">condition</tt><tt class="descclassname"> bpnumber [condition]</tt><a class="headerlink" href="#pdbcommand-condition" title="Permalink to this definition">¶</a></dt>
<dd><p>Set a new <em>condition</em> for the breakpoint, an expression which must evaluate
to true before the breakpoint is honored. If <em>condition</em> is absent, any
existing condition is removed; i.e., the breakpoint is made unconditional.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-commands">
<tt class="descname">commands</tt><tt class="descclassname"> [bpnumber]</tt><a class="headerlink" href="#pdbcommand-commands" title="Permalink to this definition">¶</a></dt>
<dd><p>Specify a list of commands for breakpoint number <em>bpnumber</em>. The commands
themselves appear on the following lines. Type a line containing just
<tt class="docutils literal"><span class="pre">end</span></tt> to terminate the commands. An example:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">commands</span> <span class="mi">1</span>
<span class="p">(</span><span class="n">com</span><span class="p">)</span> <span class="nb">print</span> <span class="n">some_variable</span>
<span class="p">(</span><span class="n">com</span><span class="p">)</span> <span class="n">end</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p>To remove all commands from a breakpoint, type commands and follow it
immediately with <tt class="docutils literal"><span class="pre">end</span></tt>; that is, give no commands.</p>
<p>With no <em>bpnumber</em> argument, commands refers to the last breakpoint set.</p>
<p>You can use breakpoint commands to start your program up again. Simply use
the continue command, or step, or any other command that resumes execution.</p>
<p>Specifying any command resuming execution (currently continue, step, next,
return, jump, quit and their abbreviations) terminates the command list (as if
that command was immediately followed by end). This is because any time you
resume execution (even with a simple next or step), you may encounter another
breakpoint–which could have its own command list, leading to ambiguities about
which list to execute.</p>
<p>If you use the ‘silent’ command in the command list, the usual message about
stopping at a breakpoint is not printed. This may be desirable for breakpoints
that are to print a specific message and then continue. If none of the other
commands print anything, you see no sign that the breakpoint was reached.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-step">
<tt class="descname">s(tep)</tt><a class="headerlink" href="#pdbcommand-step" title="Permalink to this definition">¶</a></dt>
<dd><p>Execute the current line, stop at the first possible occasion (either in a
function that is called or on the next line in the current function).</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-next">
<tt class="descname">n(ext)</tt><a class="headerlink" href="#pdbcommand-next" title="Permalink to this definition">¶</a></dt>
<dd><p>Continue execution until the next line in the current function is reached or
it returns. (The difference between <a class="reference internal" href="#pdbcommand-next"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">next</span></tt></a> and <a class="reference internal" href="#pdbcommand-step"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">step</span></tt></a> is
that <a class="reference internal" href="#pdbcommand-step"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">step</span></tt></a> stops inside a called function, while <a class="reference internal" href="#pdbcommand-next"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">next</span></tt></a>
executes called functions at (nearly) full speed, only stopping at the next
line in the current function.)</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-until">
<tt class="descname">unt(il)</tt><tt class="descclassname"> [lineno]</tt><a class="headerlink" href="#pdbcommand-until" title="Permalink to this definition">¶</a></dt>
<dd><p>Without argument, continue execution until the line with a number greater
than the current one is reached.</p>
<p>With a line number, continue execution until a line with a number greater or
equal to that is reached. In both cases, also stop when the current frame
returns.</p>
<p class="versionchanged">
<span class="versionmodified">Changed in version 3.2: </span>Allow giving an explicit line number.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-return">
<tt class="descname">r(eturn)</tt><a class="headerlink" href="#pdbcommand-return" title="Permalink to this definition">¶</a></dt>
<dd><p>Continue execution until the current function returns.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-continue">
<tt class="descname">c(ont(inue))</tt><a class="headerlink" href="#pdbcommand-continue" title="Permalink to this definition">¶</a></dt>
<dd><p>Continue execution, only stop when a breakpoint is encountered.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-jump">
<tt class="descname">j(ump)</tt><tt class="descclassname"> lineno</tt><a class="headerlink" href="#pdbcommand-jump" title="Permalink to this definition">¶</a></dt>
<dd><p>Set the next line that will be executed. Only available in the bottom-most
frame. This lets you jump back and execute code again, or jump forward to
skip code that you don’t want to run.</p>
<p>It should be noted that not all jumps are allowed – for instance it is not
possible to jump into the middle of a <a class="reference internal" href="../reference/compound_stmts.html#for"><tt class="xref std std-keyword docutils literal"><span class="pre">for</span></tt></a> loop or out of a
<a class="reference internal" href="../reference/compound_stmts.html#finally"><tt class="xref std std-keyword docutils literal"><span class="pre">finally</span></tt></a> clause.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-list">
<tt class="descname">l(ist)</tt><tt class="descclassname"> [first[, last]]</tt><a class="headerlink" href="#pdbcommand-list" title="Permalink to this definition">¶</a></dt>
<dd><p>List source code for the current file. Without arguments, list 11 lines
around the current line or continue the previous listing. With <tt class="docutils literal"><span class="pre">.</span></tt> as
argument, list 11 lines around the current line. With one argument,
list 11 lines around at that line. With two arguments, list the given range;
if the second argument is less than the first, it is interpreted as a count.</p>
<p>The current line in the current frame is indicated by <tt class="docutils literal"><span class="pre">-></span></tt>. If an
exception is being debugged, the line where the exception was originally
raised or propagated is indicated by <tt class="docutils literal"><span class="pre">>></span></tt>, if it differs from the current
line.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.2: </span>The <tt class="docutils literal"><span class="pre">>></span></tt> marker.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-ll">
<tt class="descname">ll</tt><tt class="descclassname"> | longlist</tt><a class="headerlink" href="#pdbcommand-ll" title="Permalink to this definition">¶</a></dt>
<dd><p>List all source code for the current function or frame. Interesting lines
are marked as for <a class="reference internal" href="#pdbcommand-list"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">list</span></tt></a>.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.2.</span></p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-args">
<tt class="descname">a(rgs)</tt><a class="headerlink" href="#pdbcommand-args" title="Permalink to this definition">¶</a></dt>
<dd><p>Print the argument list of the current function.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-print">
<tt class="descname">p(rint)</tt><tt class="descclassname"> expression</tt><a class="headerlink" href="#pdbcommand-print" title="Permalink to this definition">¶</a></dt>
<dd><p>Evaluate the <em>expression</em> in the current context and print its value.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-pp">
<tt class="descname">pp</tt><tt class="descclassname"> expression</tt><a class="headerlink" href="#pdbcommand-pp" title="Permalink to this definition">¶</a></dt>
<dd><p>Like the <a class="reference internal" href="#pdbcommand-print"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">print</span></tt></a> command, except the value of the expression is
pretty-printed using the <a class="reference internal" href="pprint.html#module-pprint" title="pprint: Data pretty printer."><tt class="xref py py-mod docutils literal"><span class="pre">pprint</span></tt></a> module.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-whatis">
<tt class="descname">whatis</tt><tt class="descclassname"> expression</tt><a class="headerlink" href="#pdbcommand-whatis" title="Permalink to this definition">¶</a></dt>
<dd><p>Print the type of the <em>expression</em>.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-source">
<tt class="descname">source</tt><tt class="descclassname"> expression</tt><a class="headerlink" href="#pdbcommand-source" title="Permalink to this definition">¶</a></dt>
<dd><p>Try to get source code for the given object and display it.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.2.</span></p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-display">
<tt class="descname">display</tt><tt class="descclassname"> [expression]</tt><a class="headerlink" href="#pdbcommand-display" title="Permalink to this definition">¶</a></dt>
<dd><p>Display the value of the expression if it changed, each time execution stops
in the current frame.</p>
<p>Without expression, list all display expressions for the current frame.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.2.</span></p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-undisplay">
<tt class="descname">undisplay</tt><tt class="descclassname"> [expression]</tt><a class="headerlink" href="#pdbcommand-undisplay" title="Permalink to this definition">¶</a></dt>
<dd><p>Do not display the expression any more in the current frame. Without
expression, clear all display expressions for the current frame.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.2.</span></p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-interact">
<tt class="descname">interact</tt><a class="headerlink" href="#pdbcommand-interact" title="Permalink to this definition">¶</a></dt>
<dd><p>Start an interative interpreter (using the <a class="reference internal" href="code.html#module-code" title="code: Facilities to implement read-eval-print loops."><tt class="xref py py-mod docutils literal"><span class="pre">code</span></tt></a> module) whose global
namespace contains all the (global and local) names found in the current
scope.</p>
<p class="versionadded">
<span class="versionmodified">New in version 3.2.</span></p>
</dd></dl>
<span class="target" id="debugger-aliases"></span><dl class="pdbcommand">
<dt id="pdbcommand-alias">
<tt class="descname">alias</tt><tt class="descclassname"> [name [command]]</tt><a class="headerlink" href="#pdbcommand-alias" title="Permalink to this definition">¶</a></dt>
<dd><p>Create an alias called <em>name</em> that executes <em>command</em>. The command must
<em>not</em> be enclosed in quotes. Replaceable parameters can be indicated by
<tt class="docutils literal"><span class="pre">%1</span></tt>, <tt class="docutils literal"><span class="pre">%2</span></tt>, and so on, while <tt class="docutils literal"><span class="pre">%*</span></tt> is replaced by all the parameters.
If no command is given, the current alias for <em>name</em> is shown. If no
arguments are given, all aliases are listed.</p>
<p>Aliases may be nested and can contain anything that can be legally typed at
the pdb prompt. Note that internal pdb commands <em>can</em> be overridden by
aliases. Such a command is then hidden until the alias is removed. Aliasing
is recursively applied to the first word of the command line; all other words
in the line are left alone.</p>
<p>As an example, here are two useful aliases (especially when placed in the
<tt class="file docutils literal"><span class="pre">.pdbrc</span></tt> file):</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="c"># Print instance variables (usage "pi classInst")</span>
<span class="n">alias</span> <span class="n">pi</span> <span class="k">for</span> <span class="n">k</span> <span class="ow">in</span> <span class="o">%</span><span class="mf">1.</span><span class="n">__dict__</span><span class="o">.</span><span class="n">keys</span><span class="p">():</span> <span class="nb">print</span><span class="p">(</span><span class="s">"%1."</span><span class="p">,</span><span class="n">k</span><span class="p">,</span><span class="s">"="</span><span class="p">,</span><span class="o">%</span><span class="mf">1.</span><span class="n">__dict__</span><span class="p">[</span><span class="n">k</span><span class="p">])</span>
<span class="c"># Print instance variables in self</span>
<span class="n">alias</span> <span class="n">ps</span> <span class="n">pi</span> <span class="bp">self</span>
</pre></div>
</div>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-unalias">
<tt class="descname">unalias</tt><tt class="descclassname"> name</tt><a class="headerlink" href="#pdbcommand-unalias" title="Permalink to this definition">¶</a></dt>
<dd><p>Delete the specified alias.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-!">
<tt class="descname">!</tt><tt class="descclassname"> statement</tt><a class="headerlink" href="#pdbcommand-!" title="Permalink to this definition">¶</a></dt>
<dd><p>Execute the (one-line) <em>statement</em> in the context of the current stack frame.
The exclamation point can be omitted unless the first word of the statement
resembles a debugger command. To set a global variable, you can prefix the
assignment command with a <a class="reference internal" href="../reference/simple_stmts.html#global"><tt class="xref std std-keyword docutils literal"><span class="pre">global</span></tt></a> statement on the same line,
e.g.:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="k">global</span> <span class="n">list_options</span><span class="p">;</span> <span class="n">list_options</span> <span class="o">=</span> <span class="p">[</span><span class="s">'-l'</span><span class="p">]</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-run">
<tt class="descname">run</tt><tt class="descclassname"> [args ...]</tt><a class="headerlink" href="#pdbcommand-run" title="Permalink to this definition">¶</a></dt>
<dt id="pdbcommand-restart">
<tt class="descname">restart</tt><tt class="descclassname"> [args ...]</tt><a class="headerlink" href="#pdbcommand-restart" title="Permalink to this definition">¶</a></dt>
<dd><p>Restart the debugged Python program. If an argument is supplied, it is split
with <a class="reference internal" href="shlex.html#module-shlex" title="shlex: Simple lexical analysis for Unix shell-like languages."><tt class="xref py py-mod docutils literal"><span class="pre">shlex</span></tt></a> and the result is used as the new <a class="reference internal" href="sys.html#sys.argv" title="sys.argv"><tt class="xref py py-data docutils literal"><span class="pre">sys.argv</span></tt></a>.
History, breakpoints, actions and debugger options are preserved.
<a class="reference internal" href="#pdbcommand-restart"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">restart</span></tt></a> is an alias for <a class="reference internal" href="#pdbcommand-run"><tt class="xref std std-pdbcmd docutils literal"><span class="pre">run</span></tt></a>.</p>
</dd></dl>
<dl class="pdbcommand">
<dt id="pdbcommand-quit">
<tt class="descname">q(uit)</tt><a class="headerlink" href="#pdbcommand-quit" title="Permalink to this definition">¶</a></dt>
<dd><p>Quit from the debugger. The program being executed is aborted.</p>
</dd></dl>
<p class="rubric">Footnotes</p>
<table class="docutils footnote" frame="void" id="id3" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
<tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td>Whether a frame is considered to originate in a certain module
is determined by the <tt class="docutils literal"><span class="pre">__name__</span></tt> in the frame globals.</td></tr>
</tbody>
</table>
</div>
</div>
</div>
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<li><a class="reference internal" href="#">26.2. <tt class="docutils literal"><span class="pre">pdb</span></tt> — The Python Debugger</a><ul>
<li><a class="reference internal" href="#debugger-commands">26.2.1. Debugger Commands</a></li>
</ul>
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