modules.md

Python by Example: Modules

A module is a .py file. It lets you organize code and reuse it across programs. Use import to load a module; use from ... import to bring specific names into your scope. The module name is the filename without .py. Python finds modules in the current directory and in sys.path.

What you'll learn:

• import module vs from module import name
• Accessing module contents with dot notation
• Aliasing with as

# Import entire module
import math
print(math.sqrt(16))
print(math.pi)

# Import specific names
from math import sqrt, pi
print(sqrt(9))
print(pi)

# Import with alias
import math as m
print(m.floor(3.7))

# Import everything (generally avoid)
# from math import *

import math loads the module; you access names with math.sqrt. from math import sqrt brings sqrt into the current scope—no prefix needed. Avoid from x import *; it pollutes the namespace and can hide names.

To run this program:

$ python source/modules.py
4.0
3.141592653589793
3.0
3.141592653589793
3

Tip: Use import module when you use many names from the module; use from module import x, y when you need just a few.

Try it: Create a file mymath.py with a function, then import and call it from another file.

Source: modules.py

Next: Packages