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Modules Python By Example Skip to main content Python By ExampleJourneys About

Modules

Modules organize code into namespaces and expose reusable definitions.

Importing a module gives access to its namespace. The math. prefix makes it clear where pi came from.

Source

import math

radius = 3
area = math.pi * radius ** 2
print(round(area, 2))

Output

28.27

A focused from ... import ... brings one definition into the current namespace. This keeps a common operation concise without importing every name.

Source

from statistics import mean

scores = [8, 10, 9]
print(mean(scores))

Output

Modules are objects too. Their attributes include metadata such as __name__, which records the module's import name.

Source

print(math.__name__)

Output

math

Imported modules are cached in sys.modules. Later imports reuse the module object instead of executing the file again.

Source

import sys
print("math" in sys.modules)

Output

True

Notes

Prefer plain import module when the namespace improves readability.
Use focused imports for a small number of clear names.
Place imports near the top of the file.
Imports execute module top-level code once, then reuse the cached module object.

Run the complete example

28.27
9
math
True

Execution time appears here after you run the example.

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