+++ slug = "modules" title = "Modules" section = "Modules" summary = "Modules organize code into namespaces and expose reusable definitions." doc_path = "/tutorial/modules.html" see_also = [ "import-aliases", "packages", ] +++

Modules organize Python code into files and namespaces. import executes a module once, stores it in Python's import cache, and gives your program access to its definitions.

This page focuses on import forms and module namespaces. Package layout, aliases, and dynamic imports have their own neighboring examples.

Use module namespaces such as math.sqrt when the source of a name should stay visible. Use focused imports such as from statistics import mean when the imported name is clear at the call site.

:::program

import math
import sys
from statistics import mean

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

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

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

:::

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

import math

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

28.27

:::

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

from statistics import mean

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

9

:::

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

print(math.__name__)

math

:::

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

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

True

:::

:::note

• 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. :::