09 Modules

Modules #

Introduction #

A module is a Python file containing definitions and statements that can be reused in other Python programs. Why?

  • Organize code.
  • Promote code reuse.
    • If you don’t you allow bugs to multiply and you’ll have to fix them wheever you copied the code.
  • Use built-in functionalities provided by Python and the community.
    • Saves a lot of effort
    • Allows for RAD (Rapid Application Development)

Create #

Create a file called math_utils.py:

def add(a, b):
    return a + b

def multiply(a, b):
    return a * b

Use #

Import and use modules from math_utils.py

import math_utils

print(math_utils.add(3, 5))
print(math_utils.multiply(4, 6))

Different way:

from math_utils import add
print(add(2, 3))

Activity: create a simple module string_utils.py with functions like to_uppercase, to_lowercase, and use it in another script.

Batteries Included: Python Standard Library #

Python comes with a rich set of pre-installed modules for various tasks. Here the documentation.

Some famous modules:

  • math
import math
print(math.sqrt(16))
print(math.pi)
  • datetime
from datetime import datetime
now = datetime.now()
print(f"Current time: {now}")
  • random
>>> import random
>>> random.randint(1, 100)
22
>>> random.choice(["Peter", "John", "Jane"])
'Jane'
>>>
  • os Provides a way to interact with the operating system.
    • Work with the FS (file system).
    • Retrieve and set environment variables
    • Run shell commands
import os
print(os.getcwd())  # Get current directory
  • json
import json
data = {"name": "Alice", "age": 25}
json_string = json.dumps(data)
print(json_string)

Activity (7 min):

  • Use math module to calculate the square root of a number.
  • Use random module to generate a random number between 1 and 50.
  • Use datetime module to display the current date and time.

Other mentions:

  • shutil - High-level operations on files and directories. Used for copying, moving, and removing files or entire directories.
  • copy - Provides functions to copy objects in Python. Supports both deep and shallow copies.
  • time - Functions for working with time and delays. Provides utilities to measure execution time, format time, and create delays.
  • sys - Provides access to system-specific parameters and functions. Often used to access CLI arguments.
  • re - Provides support for regular expressions (regex) to work with text patterns. Used for powerful pattern matching, searching, and replacing strings.
  • argparse - Used for creating user-friendly command-line interfaces.
  • itertools - Provides a collection of fast and memory-efficient tools for working with iterators. Useful for looping, generating combinations, permutations, and more.
  • decimal - the library if you need to work with decimal numbers without losing precision

PyPI #

The Python Package Index (PyPI) is a repository of software for the Python programming language.

This is how you install packages from there:

pip install requests

And then you can start using them in your programs:

import requests
response = requests.get("https://api.github.com")
print(response.json())

Homework (graded) #

Calculator #

Create a library called math_lib.py with functions: add, subtract, multiply, and divide. Write a script (calculator.py) that imports and uses this module.

PyPI (optional) #

Install the requests library. Use it to fetch the current weather for your city from a free API (e.g., OpenWeatherMap).

Edit Edit this page