Modules in Python

A Module is simply a Python file (e.g., mymodule.py) that contains functions, variables, and classes. Instead of writing all your code in one massive file, you can split it into multiple modules to keep it clean and organized.

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16.1.1 Creating & Importing a Module

Let us create a simple calculator module.

Create a file named calculator.py:

# calculator.py
def add(x, y):
    return x + y

def subtract(x, y):
    return x - y

Now, we can import this file and use its functions in another file, say main.py:

# main.py
import calculator

result = calculator.add(10, 5)
print("Result:", result) # Output: Result: 15

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16.1.2 Ways to Import in Python

Python provides different ways to import module items:

1. import module_name

Imports the entire module. You must prefix all functions with the module name when calling them.

import math
print(math.sqrt(25)) # Output: 5.0

2. from module import specific_item

Imports only a specific function or variable. You can call it directly without the module name prefix.

from math import sqrt
print(sqrt(16)) # Output: 4.0

3. import module_name as alias

Renames the imported module to a shorter nickname (alias). This is extremely common in data science.

import datetime as dt
print(dt.datetime.now())

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16.1.3 Useful Built-in Modules

Python comes with a "batteries included" philosophy, meaning it includes pre-written modules for common tasks:

• math: Mathematical operations (like sqrt, pi, sin).
• random: Generating random numbers and selections.
• datetime: Handling calendar dates and clock times.
• os: Directory creations, path checking, and OS tasks.

import random
import os

# Select a random item from a list
fruits = ["Apple", "Banana", "Cherry"]
print("Random choice:", random.choice(fruits))

# Check the current working folder path
current_dir = os.getcwd()
print("Working folder:", current_dir)