# 3.20 Standard Module `user`

As a policy, Python doesn't run user-specified code on startup of Python programs. (Only interactive sessions execute the script specified in the `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

The `user` module looks for a file ``.pythonrc.py`' in the user's home directory and if it can be opened, exececutes it (using `execfile()`) in its own (i.e. the module `user`'s) global namespace. Errors during this phase are not caught; that's up to the program that imports the `user` module, if it wishes. The home directory is assumed to be named by the `HOME` environment variable; if this is not set, the current directory is used.

The user's ``.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 ``.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 ``.pythonrc.py`' file that you test in your module. For example, a module `spam` that has a verbosity level can look for a variable `user.spam_verbose`, as follows:

    import user
    try:
        verbose = user.spam_verbose  # user's verbosity preference
    except AttributeError:
        verbose = 0                  # default verbosity

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 a program by placing arbitrary code in the ``.pythonrc.py`' file.

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

For a site-wide customization mechanism, see module `site`.