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author | Georg Brandl <georg@python.org> | 2007-08-15 14:28:01 (GMT) |
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committer | Georg Brandl <georg@python.org> | 2007-08-15 14:28:01 (GMT) |
commit | 8ec7f656134b1230ab23003a94ba3266d7064122 (patch) | |
tree | bc730d5fb3302dc375edd26b26f750d609b61d72 /Doc/library/user.rst | |
parent | f56181ff53ba00b7bed3997a4dccd9a1b6217b57 (diff) | |
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Move the 2.6 reST doc tree in place.
Diffstat (limited to 'Doc/library/user.rst')
-rw-r--r-- | Doc/library/user.rst | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/Doc/library/user.rst b/Doc/library/user.rst new file mode 100644 index 0000000..aa09b67 --- /dev/null +++ b/Doc/library/user.rst @@ -0,0 +1,69 @@ + +:mod:`user` --- User-specific configuration hook +================================================ + +.. module:: user + :synopsis: A standard way to reference user-specific modules. + + +.. index:: + pair: .pythonrc.py; file + triple: user; configuration; file + +As a policy, Python doesn't run user-specified code on startup of Python +programs. (Only interactive sessions execute the script specified in the +:envvar:`PYTHONSTARTUP` environment variable if it exists). + +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 :: + + import user + +.. index:: builtin: execfile + +The :mod:`user` module looks for a file :file:`.pythonrc.py` in the user's home +directory and if it can be opened, executes it (using :func:`execfile`) in its +own (the module :mod:`user`'s) global namespace. Errors during this phase are +not caught; that's up to the program that imports the :mod:`user` module, if it +wishes. The home directory is assumed to be named by the :envvar:`HOME` +environment variable; if this is not set, the current directory is used. + +The user's :file:`.pythonrc.py` could conceivably test for ``sys.version`` if it +wishes to do different things depending on the Python version. + +A warning to users: be very conservative in what you place in your +:file:`.pythonrc.py` 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. + +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 +:file:`.pythonrc.py` file that you test in your module. For example, a module +:mod:`spam` that has a verbosity level can look for a variable +``user.spam_verbose``, as follows:: + + import user + + verbose = bool(getattr(user, "spam_verbose", 0)) + +(The three-argument form of :func:`getattr` is used in case the user has not +defined ``spam_verbose`` in their :file:`.pythonrc.py` file.) + +Programs with extensive customization needs are better off reading a +program-specific customization file. + +Programs with security or privacy concerns should *not* import this module; a +user can easily break into a program by placing arbitrary code in the +:file:`.pythonrc.py` file. + +Modules for general use should *not* import this module; it may interfere with +the operation of the importing program. + + +.. seealso:: + + Module :mod:`site` + Site-wide customization mechanism. + |