Import modules
Python has a way to put definitions in a file and use them in a script or in an interactive instance of the interpreter. The file is called a Python module. You can import definitions from a Python module into other programs or other Python modules.
For example, the factorial() function isn't one of the standard functions built into Python. It's part of the Python math module. So, when we run factorial() before importing the math module, we get an error:
factorial(5)
The error output is:
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-147-637175d621a4> in <module>
----> 1 factorial(5)
NameError: name 'factorial' is not defined
However, the situation changes after we import the Python math module:
import math
math.factorial(5)
The output is:
120
Notice that we still have to prepend math to the factorial() function call. We can use a different method to import only that specific function from the Python math module and use it as if it were defined in our program:
from math import factorial
factorial(5)
The output is:
120
You can add more cells to your notebook by selecting insert cell below (+) at the top of the window. The Python math module has many functions in it. Try importing some of the other math functions and playing around with them.
Takeaway
You'll use several Python modules regularly in conducting data science in Python, so understanding how to import them is essential, especially in this training.