SAVING YOUR CODE IN A MODULE
Earlier you saw how to launch the Python interpreter from the command line and then enter Python commands. However, that everything that you type in the Python interpreter is only valid for the current session: if you exit the interpreter and then launch the interpreter again, your previous definitions are no longer valid. Fortunately, Python enables you to store code in a text file, as discussed in the next section.
A module in Python is a text file that contains Python statements. In the previous section, you saw how the Python interpreter enables you to test code snippets whose definitions are valid for the current session. If you want to retain the code snippets and other definitions, place them in a text file so that you can execute that code outside of the Python interpreter.
The outermost statements in a Python are executed from top to bottom when the module is imported for the first time, which will then set up its variables and functions.
A Python...
