Learning Python

Python Configuration Details

So far, we’ve seen how to make the Python interpreter execute programs we’ve typed. But besides the interpreter, a Python installation also comes with a collection of utility programs, stored in the Python source library. Moreover, the Python interpreter recognizes settings in the system shell’s environment, which let us tailor the interpreter’s behavior (where it finds the source-code files, for example). This section talks about the environment settings commonly used by Python programmers, peeks at Python installation details, and presents an example script that illustrates most of the configuration steps you’ll probably need to know about. If you have access to a ready-to-run Python, you can probably skip much of this section, or postpone it for a later time.

Environment Variables

The Python interpreter recognizes a handful of environment variable settings, but only a few are used often enough to warrant explanation here. Table 1.1 summarizes the main Python variable settings.

Table 1-1. Important Environment Variables

Role	Variable
System shell search path (for finding “python”)	PATH (or path)
Python module search path (for imports)	PYTHONPATH
Path to Python interactive startup file	PYTHONSTARTUP
GUI extension variables (Tkinter)	TCL_LIBRARY, TK_LIBRARY

These variables are straightforward to use, but here are a few pointers:

• The PATH setting lists a set of directories that the operating system searches for executable programs. It should ...