22.6. The import statement: Use a module

22.6. The `import` statement: Use a module

One of the cornerstones of Python's design philosophy is to keep the language relatively small and well-defined, and move all non-essential functionality to library modules. The import and from statements allow your programs to use items from these library modules.

Your Python installation will come with a large collection of released modules.
You can also create your own modules. Just place Python statements defining variables, functions, and classes into a file whose name ends in “.py”.

There are two different statements you can use to import items from a module:

The from statement copies items from a module into your namespace. After importing an item in this way, you can refer to the item simply by its name.
General forms:
```
from moduleName import *
from moduleName import name₁, name₂, ...
```
The first form imports all the items from the module named moduleName. If you want to import only specific items, use the second form, and enumerate the names you want from that module.
The import statement makes an entire module's content available to you as a separate namespace. To refer to some item named N in a module named M, use the dot notation, M.N.
Here is the general form:
```
import moduleName, ...
```
If you want to use some module M in this way, but you want to change the name to some different name A, use this form:
```
import M as A
```

Here are some examples that use the standard math module that is always available in a proper Python install. This module has functions such as sqrt() (square root), as well as variables such as pi. (Although π is a constant in the mathematical sense, the name pi is a variable in the Python sense.)

>>> from math import *
>>> sqrt(16)
4.0
>>> pi
3.1415926535897931

If you wanted only the sqrt function and the variable pi, this statement would do the job:

from math import sqrt, pi

Now some examples of the second form.

>>> import math
>>> math.sqrt(25)
5.0
>>> math.pi
3.1415926535897931

Suppose your program already used the name math for something else, but you still want to use functions from the math module. You can import it under a different name like this:

>>> import math as crunch
>>> crunch.sqrt(25)
5.0
>>> crunch.pi
3.1415926535897931

Python 2.7 quick reference

22.6. The import statement: Use a module

22.6. The `import` statement: Use a module