Python Core | VoidX Academy

15. Python Modules

Architecture

Python Modules

Consider a module to be the same as a code library. A module is simply a file containing a set of functions, classes, and variables that you want to include in your application.

As your programs get larger, putting all your code in one massive file becomes impossible to manage. Modules allow you to logically organize your Python code into separate files, making it easier to understand, share, and maintain.

What is a Module?

To create a module, you just save the code you want in a file with the file extension .py. For example, imagine a file named greetings.py containing a single function.

# File: greetings.py
def say_hello(name):
    print(f"Hello, {name}!")

That is it! You have created a module. You can now pull this code into other files without rewriting it.

Using a Module

To use a module in a different file, use the import statement. When you import a module, you access its functions using dot notation.

# Assuming greetings.py is in the same folder
import greetings

# We use the module name, a dot, and the function name
greetings.say_hello("Alice")

OutputHello, Alice!

Variables in Modules

Modules can contain functions, but they can also contain variables of all types (arrays, dictionaries, objects etc). Let's imagine our greetings.py file also contains a dictionary.

# File: greetings.py
user_data = {
    "name": "Bob",
    "age": 30,
    "country": "Norway"
}

We can access this variable from another file just like we accessed the function:

import greetings

age = greetings.user_data["age"]
print(f"The user is {age} years old.")

OutputThe user is 30 years old.

Renaming a Module

If a module name is too long or conflicts with an existing variable, you can create an alias when you import it by using the as keyword.

import greetings as grt

grt.say_hello("Charlie")
print(grt.user_data["country"])

OutputHello, Charlie! Norway

Import From

You can choose to import only specific parts from a module by using the from keyword. When you do this, you do not use the module name with a dot. You use the function or variable directly.

# We only want the dictionary, not the function
from greetings import user_data

# We do NOT use greetings.user_data
print(user_data["name"])

OutputBob

💡Warning: Be careful with from X import Y. If you import a variable directly and your current file already has a variable with the same name, the imported one will overwrite yours!

Built-in Modules

Python comes with a huge "Standard Library" of pre-installed modules that you can import whenever you like. You do not need to install them or create them yourself.

import platform

system = platform.system()
print(f"Running on: {system}")

OutputRunning on: Linux

The math Module

One of the most useful built-in modules is math, which provides access to advanced mathematical functions.

import math

# Square root
x = math.sqrt(64)
print(x)

# Pi constant
print(math.pi)

# Rounding up and down
print(math.ceil(1.4))   # Rounds UP to nearest integer
print(math.floor(1.4))  # Rounds DOWN to nearest integer

Output8.0 3.141592653589793 2 1

The datetime Module

Python does not have a native data type for dates, but we can import a module named datetime to work with dates as date objects.

import datetime

# Get the exact current date and time
x = datetime.datetime.now()
print(x)

# Extract specific parts
print(x.year)

# Format date into readable string (e.g., full weekday name)
print(x.strftime("%A"))

Output2026-05-22 01:35:05.123456 2026 Friday

The dir() Function

If you import a module but aren't sure what functions or variables are inside it, there is a built-in function to list all the names in a module: the dir() function.

import math

# Print a list of everything inside the math module
contents = dir(math)

# Slicing the first 5 just to keep output clean
print(contents[:5])

Output['__doc__', '__loader__', '__name__', '__package__', '__spec__']

15. Python Modules

Architecture

Python Modules

Consider a module to be the same as a code library. A module is simply a file containing a set of functions, classes, and variables that you want to include in your application.

What is a Module?

To create a module, you just save the code you want in a file with the file extension .py. For example, imagine a file named greetings.py containing a single function.

# File: greetings.py
def say_hello(name):
    print(f"Hello, {name}!")

That is it! You have created a module. You can now pull this code into other files without rewriting it.

Using a Module

To use a module in a different file, use the import statement. When you import a module, you access its functions using dot notation.

# Assuming greetings.py is in the same folder
import greetings

# We use the module name, a dot, and the function name
greetings.say_hello("Alice")

OutputHello, Alice!

Variables in Modules

Modules can contain functions, but they can also contain variables of all types (arrays, dictionaries, objects etc). Let's imagine our greetings.py file also contains a dictionary.

# File: greetings.py
user_data = {
    "name": "Bob",
    "age": 30,
    "country": "Norway"
}

We can access this variable from another file just like we accessed the function:

import greetings

age = greetings.user_data["age"]
print(f"The user is {age} years old.")

OutputThe user is 30 years old.

Renaming a Module

If a module name is too long or conflicts with an existing variable, you can create an alias when you import it by using the as keyword.

import greetings as grt

grt.say_hello("Charlie")
print(grt.user_data["country"])

OutputHello, Charlie! Norway

Import From

# We only want the dictionary, not the function
from greetings import user_data

# We do NOT use greetings.user_data
print(user_data["name"])

OutputBob

💡Warning: Be careful with from X import Y. If you import a variable directly and your current file already has a variable with the same name, the imported one will overwrite yours!

Built-in Modules

Python comes with a huge "Standard Library" of pre-installed modules that you can import whenever you like. You do not need to install them or create them yourself.

import platform

system = platform.system()
print(f"Running on: {system}")

OutputRunning on: Linux

The math Module

One of the most useful built-in modules is math, which provides access to advanced mathematical functions.

import math

# Square root
x = math.sqrt(64)
print(x)

# Pi constant
print(math.pi)

# Rounding up and down
print(math.ceil(1.4))   # Rounds UP to nearest integer
print(math.floor(1.4))  # Rounds DOWN to nearest integer

Output8.0 3.141592653589793 2 1

The datetime Module

Python does not have a native data type for dates, but we can import a module named datetime to work with dates as date objects.

import datetime

# Get the exact current date and time
x = datetime.datetime.now()
print(x)

# Extract specific parts
print(x.year)

# Format date into readable string (e.g., full weekday name)
print(x.strftime("%A"))

Output2026-05-22 01:35:05.123456 2026 Friday

The dir() Function

If you import a module but aren't sure what functions or variables are inside it, there is a built-in function to list all the names in a module: the dir() function.

import math

# Print a list of everything inside the math module
contents = dir(math)

# Slicing the first 5 just to keep output clean
print(contents[:5])

Output['__doc__', '__loader__', '__name__', '__package__', '__spec__']

15. Python Modules

Python Modules

What is a Module?

Using a Module

Variables in Modules

Renaming a Module

Import From

Built-in Modules

The math Module

The datetime Module

The dir() Function

Knowledge Check

15. Python Modules

Python Modules

What is a Module?

Using a Module

Variables in Modules

Renaming a Module

Import From

Built-in Modules

The math Module

The datetime Module

The dir() Function

Knowledge Check