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42. Importing Modules

1. Introduction​

Modules are Python files containing reusable code (functions, classes, variables).
You can import them into your program using the import statement.

2. Importing a Whole Module​

import math
print(math.sqrt(16))  # 4.0

3. Importing Specific Items​

from math import pi, sqrt
print(pi)      # 3.14159...
print(sqrt(25)) # 5.0

4. Using Aliases​

import numpy as np
print(np.array([1,2,3]))
from math import *
print(sin(0))

⚠️ Can cause name conflicts.

6. Importing Custom Modules​

If you have a file mymath.py:

# mymath.py
def square(x): return x*x

Use it in another script:

import mymath
print(mymath.square(5))

7. Reloading Modules​

Sometimes you need to reload a module (during development).

import importlib, mymath
importlib.reload(mymath)

8. Next Steps​

✅ You now know how to import modules.
In the next chapter, we’ll learn about creating your own modules.