You have seen how you can reuse code in your program by defining functions once. What if you wanted to reuse a number of functions in other programs that you write? As you might have guessed, the answer is modules. A module is basically a file containing all your functions and variables that you have defined. To reuse the module in other programs, the filename of the module must have a.py extension.
A module can be imported by another program to make use of its functionality. This is how we can use the Python standard library as well. First, we will see how to use the standard library modules.