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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 8. Python functions</title><link rel="stylesheet" type="text/css" href="style.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="home" href="index.html" title="Bakefile Manual" /><link rel="up" href="index.html" title="Bakefile Manual" /><link rel="prev" href="ch07.html" title="Chapter 7. Variables defined by Bakefile" /><link rel="next" href="ch09.html" title="Chapter 9. Format specific documentation" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 8. Python functions</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch07.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="ch09.html">Next</a></td></tr></table><hr /></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="ch.functions"></a>Chapter 8. Python functions</h1></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="section"><a href="ch08.html#sec.intro">Introduction</a></span></dt><dt><span class="section"><a href="ch08.html#sec.pyfn.howto">How to use a Python function in a bakefile</a></span></dt><dt><span class="section"><a href="ch08.html#sec.py.fn">Python functions</a></span></dt><dd><dl><dt><span class="section"><a href="ch08.html#pyfunc.envvar">envvar</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.isconst">isconst</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.isdefined">isdefined</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.isoption">isoption</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.iscondvar">iscondvar</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.ifthenelse">ifthenelse</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.ref">ref</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.isDeadTarget">isDeadTarget</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.substituteFromDict">substituteFromDict</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.nativePaths">nativePaths</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.addPrefixIfNotEmpty">addPrefixIfNotEmpty</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.addPrefixToList">addPrefixToList</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.safeSplit">safeSplit</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.fileList">fileList</a></span></dt><dt><span class="section"><a href="ch08.html#pyfunc.removeDuplicates">removeDuplicates</a></span></dt></dl></dd></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec.intro"></a>Introduction</h2></div></div></div><p>
In Bakefile, the expression inside <code class="literal">$(...)</code>
doesn't have to be a variable name, it can be
<span class="emphasis"><em>any</em></span> Python expression. Expressions that
cannot be evaluated at runtime and are translated into output
format conditions are more limited, but as long as the expression
is evaluated only at Bakefile execution time, it can be any valid
Python expression. In particular, any Python functions may be
called.
</p><p>
In order to make common tasks easier, Bakefile provides
miscellaneous utility functions which can
be used in your bakefiles. Unlike tags and
rules provided through <a class="link" href="ch10.html" title="Chapter 10. Modules">modules</a>,
the functions documented in this section are available everywhere
in Bakefile.
</p><p>
Except where explicitely stated differently, all functions accept
as arguments Python strings.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec.pyfn.howto"></a>How to use a Python function in a bakefile</h2></div></div></div><p>
Python instructions and thus also Python calls to functions, can
be used in bakefile wrapping them into the <code class="literal">$( )</code>
symbols. E.g. suppose you want to use the
<a class="xref" href="ch08.html#pyfunc.fileList" title="fileList">fileList</a> function described below to
set variable <code class="literal">A</code>; you should then write:
</p><pre class="programlisting">
<set var="A">
$(fileList('mypath/*.c'))
</set>
</pre><p>
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec.py.fn"></a>Python functions</h2></div></div></div><p>
The following Python functions are defined:
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.envvar"></a>envvar</h3></div></div></div><pre class="synopsis">envvar(<em class="parameter"><code>"name"</code></em>)</pre><p>
Returns reference to environment variable
<code class="varname">name</code>. This function should be used instead
of <code class="literal">$(DOLLAR)(name)</code> idiom, because some output
formats (namely, Watcom makefiles) use different syntax for
referencing environment variables.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.isconst"></a>isconst</h3></div></div></div><pre class="synopsis">isconst(<em class="parameter"><code>expr</code></em>)</pre><p>
Returns <code class="literal">true</code> if the
<span class="emphasis"><em>expression</em></span> (i.e. not variable name as in
the case of <a class="xref" href="ch08.html#pyfunc.isdefined" title="isdefined">isdefined</a> etc.) given as
argument is constant expression.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.isdefined"></a>isdefined</h3></div></div></div><pre class="synopsis">isdefined(<em class="parameter"><code>name</code></em>)</pre><p>
Returns <code class="literal">true</code> if the given string is the name
of an option or a (conditional) variable previously defined in the bakefile.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.isoption"></a>isoption</h3></div></div></div><pre class="synopsis">isoption(<em class="parameter"><code>name</code></em>)</pre><p>
Returns <code class="literal">true</code> if the given string is the name
of an option previously defined in the bakefile.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.iscondvar"></a>iscondvar</h3></div></div></div><pre class="synopsis">iscondvar(<em class="parameter"><code>name</code></em>)</pre><p>
Returns <code class="literal">true</code> if the given string is the name
of a conditional variable previously defined in the bakefile.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.ifthenelse"></a>ifthenelse</h3></div></div></div><pre class="synopsis">ifthenelse(<em class="parameter"><code>cond</code></em>, <em class="parameter"><code>iftrue</code></em>, <em class="parameter"><code>iffalse</code></em>)</pre><p>
Allows to write if-then-else constructs inside bakefiles. The
arguments are respectively the <span class="emphasis"><em>if condition</em></span>
(use Python syntax!), the Python expression to execute in case the
condition results true and the Python expression to execute in
case the condition results false.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.ref"></a>ref</h3></div></div></div><pre class="synopsis">ref(<em class="parameter"><code>var</code></em>, <em class="parameter"><code>target=None</code></em>)</pre><p>
Creates a reference to the given <em class="parameter"><code>var</code></em> variable
which will be evaluated only in the final stage of bakefile
processing.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.isDeadTarget"></a>isDeadTarget</h3></div></div></div><pre class="synopsis">isDeadTarget(<em class="parameter"><code>target</code></em>)</pre><p>
Returns <span class="emphasis"><em>true</em></span> if the given string is the name
of a conditional target whose condition is never met.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.substituteFromDict"></a>substituteFromDict</h3></div></div></div><pre class="synopsis">substituteFromDict(<em class="parameter"><code>var</code></em>, <em class="parameter"><code>dict</code></em>, <em class="parameter"><code>desc=None</code></em>)</pre><p>
Returns the <span class="emphasis"><em>value</em></span> of the dictionary entry
whose <span class="emphasis"><em>key</em></span> matches the value of the variable
or option named <em class="parameter"><code>var</code></em>.
E.g.
</p><pre class="programlisting">
<set var="A">
$(substituteFromDict(OPTION,{'1':'value1','0':'value0'}))
</set>
</pre><p>
sets <span class="emphasis"><em>A</em></span> to <span class="emphasis"><em>value1</em></span> if
<span class="emphasis"><em>OPTION</em></span> is <span class="emphasis"><em>1</em></span> or to
<span class="emphasis"><em>value2</em></span> if <span class="emphasis"><em>OPTION</em></span> is
<span class="emphasis"><em>0</em></span>.
Note that Python requires curly brackets to define a dictionary.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.nativePaths"></a>nativePaths</h3></div></div></div><pre class="synopsis">nativePaths(<em class="parameter"><code>filenames</code></em>)</pre><p>
Returns the given string with the <code class="literal">/</code> characters
substituted by the content of the <a class="xref" href="ch07.html#var.DIRSEP">DIRSEP</a>
variable (see the Variables section).
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.addPrefixIfNotEmpty"></a>addPrefixIfNotEmpty</h3></div></div></div><pre class="synopsis">addPrefixIfNotEmpty(<em class="parameter"><code>prefix</code></em>, <em class="parameter"><code>value</code></em>)</pre><p>
Returns the <em class="parameter"><code>value</code></em> string prefixed with
<em class="parameter"><code>prefix</code></em>, unless <em class="parameter"><code>value</code></em> is
empty.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.addPrefixToList"></a>addPrefixToList</h3></div></div></div><pre class="synopsis">addPrefixToList(<em class="parameter"><code>prefix</code></em>, <em class="parameter"><code>value</code></em>)</pre><p>
Adds <em class="parameter"><code>prefix</code></em> to every item in
<em class="parameter"><code>value</code></em> interpreted as whitespace-separated
list.
E.g.
</p><pre class="programlisting">
<set var="A">
$(addPrefixToList('file','1.txt 2.txt 3.txt'))
</set>
</pre><p>
sets the <span class="emphasis"><em>A</em></span> variable to <code class="literal">file1.txt file2.txt file3.txt</code>
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.safeSplit"></a>safeSplit</h3></div></div></div><pre class="synopsis">safeSplit(<em class="parameter"><code>str</code></em>)</pre><p>
Splits the given string like the built-in split() Python function
but, unlike the Python <code class="literal">split()</code> function,
recognizes that an expression like
</p><pre class="programlisting">
"$(myPythonFuncCall(arg1, arg2)) item2"
</pre><p>
must be split as
</p><pre class="programlisting">
[ "$(myPythonFuncCall(arg1, arg2))", "item2" ]
</pre><p>
and not as the built-in split() function would do
</p><pre class="programlisting">
[ "$(myPythonFuncCall(arg1,", "arg2))", "item2" ]
</pre><p>
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.fileList"></a>fileList</h3></div></div></div><pre class="synopsis">fileList(<em class="parameter"><code>path</code></em>)</pre><p>
Returns a string containing a space-separed list of all files
found in the given <em class="parameter"><code>path</code></em>.
<em class="parameter"><code>path</code></em> typically is a relative path
(absolute paths should be avoided in well-designed bakefiles)
with a mask used to match only wanted files.
</p><p>
When the given path is relative, it must be relative to the
<a class="xref" href="ch07.html#var.SRCDIR">SRCDIR</a>
global variable; remember that <a class="xref" href="ch07.html#var.SRCDIR">SRCDIR</a>
is in turn relative to
the location of the generated makefile
(see <a class="xref" href="ch07.html#var.OUTPUT_FILE">OUTPUT_FILE</a>).
</p><p>
Additionally this function can accept Python lists of strings,
too. The returned value is the list of all files found in all
the paths of the list.
E.g.
</p><pre class="programlisting">
<sources>$(fileList('../src/*.cpp'))</sources>
<sources>$(fileList(['../src/*.cpp', '../src/*.c']))</sources>
</pre><p>
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="pyfunc.removeDuplicates"></a>removeDuplicates</h3></div></div></div><pre class="synopsis">removeDuplicates(<em class="parameter"><code>list</code></em>)</pre><p>
Returns a copy of the given (space-separed) list with all
duplicate tokens removed.
</p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch07.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="ch09.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 7. Variables defined by Bakefile </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 9. Format specific documentation</td></tr></table></div></body></html>
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