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<title>3.31 user -- User-specific configuration hook</title>
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<H1><A NAME="SECTION0053100000000000000000">
3.31 <tt class="module">user</tt> --
         User-specific configuration hook</A>
</H1>

<P>
<A NAME="module-user"></A>

<P>
<a id='l2h-808' xml:id='l2h-808'></a><a id='l2h-809' xml:id='l2h-809'></a>
<P>
As a policy, Python doesn't run user-specified code on startup of
Python programs.  (Only interactive sessions execute the script
specified in the <a class="envvar" id='l2h-811' xml:id='l2h-811'>PYTHONSTARTUP</a> environment variable if it
exists).

<P>
However, some programs or sites may find it convenient to allow users
to have a standard customization file, which gets run when a program
requests it.  This module implements such a mechanism.  A program
that wishes to use the mechanism must execute the statement

<P>
<div class="verbatim"><pre>
import user
</pre></div>

<P>
The <tt class="module">user</tt> module looks for a file <span class="file">.pythonrc.py</span> in the user's
home directory and if it can be opened, executes it (using
<tt class="function">execfile()</tt><a id='l2h-810' xml:id='l2h-810'></a>) in its own (the
module <tt class="module">user</tt>'s) global namespace.  Errors during this phase
are not caught; that's up to the program that imports the
<tt class="module">user</tt> module, if it wishes.  The home directory is assumed to
be named by the <a class="envvar" id='l2h-812' xml:id='l2h-812'>HOME</a> environment variable; if this is not set,
the current directory is used.

<P>
The user's <span class="file">.pythonrc.py</span> could conceivably test for
<code>sys.version</code> if it wishes to do different things depending on
the Python version.

<P>
A warning to users: be very conservative in what you place in your
<span class="file">.pythonrc.py</span> file.  Since you don't know which programs will
use it, changing the behavior of standard modules or functions is
generally not a good idea.

<P>
A suggestion for programmers who wish to use this mechanism: a simple
way to let users specify options for your package is to have them
define variables in their <span class="file">.pythonrc.py</span> file that you test in
your module.  For example, a module <tt class="module">spam</tt> that has a verbosity
level can look for a variable <code>user.spam_verbose</code>, as follows:

<P>
<div class="verbatim"><pre>
import user

verbose = bool(getattr(user, "spam_verbose", 0))
</pre></div>

<P>
(The three-argument form of <tt class="function">getattr()</tt> is used in case
the user has not defined <code>spam_verbose</code> in their
<span class="file">.pythonrc.py</span> file.)

<P>
Programs with extensive customization needs are better off reading a
program-specific customization file.

<P>
Programs with security or privacy concerns should <em>not</em> import
this module; a user can easily break into a program by placing
arbitrary code in the <span class="file">.pythonrc.py</span> file.

<P>
Modules for general use should <em>not</em> import this module; it may
interfere with the operation of the importing program.

<P>
<div class="seealso">
  <p class="heading">See Also:</p>

  <dl compact="compact" class="seemodule">
    <dt>Module <b><tt class="module"><a href="module-site.html">site</a></tt>:</b>
    <dd>Site-wide customization mechanism.
  </dl>
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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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