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Python 3

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The Universe of Modules
Home >>> Online Lessons, Python 3

Python Standard Library

We have already used the random and turtle modules to generate random numbers or to create graphical effects using the turtle. These are part of the Python 3 Standard Library, which contains many other useful modules:

https://docs.python.org/3/library/

We can't analyze all of them here; we just need to be aware of their existence and, if needed, properly document ourselves, then use the subroutines of a particular module that can be useful to us!

Ways to Include Modules

To include a module in our program, we've seen that we use the import directive followed by the library name:

import random

We can include multiple modules in a single command:

import random, turtle

or just some of the subroutines contained in a module:

from random import random, randint, choice

because we want to be efficientwe include only what we need.

The math Module - Be Self-Taught!

Let's assume we need to calculate the expression:

G(x) = sin(x) + cos(x) + cos(2*x)

for x, a value read from the keyboard.

First, I try a simple formula in the console:



but I immediately notice that the cosine function is not provided by default by the Python 3 interpreter. I open the standard library web page and notice that there is a math module:



Wonderful! There, besides cos, I find a lot of other useful mathematical functions and study a bit about them (there are dozens, and I might need one of them later).

I return to my program and first import the module, then write the rest of the code that solves the problem:



You can download the source code from [here].

Of course, it would have been optimal to include only the functions used from the module:

from math import sin, cos

Simple and elegant.
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