Objective

In this unit, we will explore some of the most commonly used modules in Python's standard library. These modules provide a wide range of functionalities that can enhance your programs without the need to install external packages. By the end of this unit, you'll be familiar with several key modules and how to use them in your Python projects.

Python Standard Library

Python's standard library is a collection of modules and packages that come bundled with Python. It provides a wide range of functionalities, from mathematical computations to file handling, regular expressions, and more. The standard library is one of Python's greatest strengths, offering tools and functions that facilitate rapid development without the need to search for third-party libraries.

Math Module (Documentation)

The math module provides mathematical functions and constants.

Example: Calculating the square root of 16.

import math

sqrt_value = math.sqrt(16)
print(sqrt_value)  # Output: 4.0

The math.sqrt function calculates the square root of the given number.

Random Module (Documentation)

The random module allows you to generate random numbers and make random choices.

Example: Picking a random element from a list.

import random

choices = ['apple', 'banana', 'cherry']
picked_fruit = random.choice(choices)
print(picked_fruit)  # Output: a randomly picked fruit

The random.choice function picks a random element from the given list.

Datetime Module (Documentation)

The datetime module helps you work with dates and times.

Example: Getting the current date.

import datetime

current_date = datetime.date.today()
print(current_date)  # Output: current date

The datetime.date.today function returns the current date.

OS Module (Documentation)

The os module provides functions to interact with the operating system, such as file manipulation.

Example: Renaming a file.

import os

os.rename('old_file.txt', 'new_file.txt')

The os.rename function renames the file from 'old_file.txt' to 'new_file.txt'.

JSON Module (Documentation)

The json module helps you work with JSON data.

Example: Converting a dictionary to a JSON string.

import json

data = {'name': 'John', 'age': 30}
json_str = json.dumps(data)
print(json_str)  # Output: '{"name": "John", "age": 30}'

The json.dumps function converts a Python dictionary into a JSON string.

IO Module (Documentation)

The io module helps with file I/O operations.

Example: Writing and reading a string to/from an in-memory text stream.

import io

content = "This is a content."
file = io.StringIO(content)
print(file.read())  # Output: This is a content.

The io.StringIO function creates an in-memory text stream, and the read method reads the content.

RE Module (Documentation)

The re module provides regular expression matching operations.

Example: Finding all numbers in a string.

import re

pattern = re.compile(r'\d+')
matches = pattern.findall('12 apples and 34 bananas')
print(matches)  # Output: ['12', '34']

The re.compile function compiles a regular expression pattern, and the findall method finds all occurrences of the pattern in the given string. In this case, it finds all sequences of digits.

Combining Modules

You can combine these modules to create more complex programs. For example, you can use the random module to randomly pick a date from a list, and the datetime module to format it:

import random
import datetime

dates = [datetime.date(2023, 7, 28), datetime.date(2022, 5, 15), datetime.date(2021, 1, 10)]
picked_date = random.choice(dates)
formatted_date = picked_date.strftime("%B %d, %Y")
print(formatted_date)  # Output: a randomly picked formatted date

Project: Enhance Your Turtle Drawing Program Using Functions from the Python Standard Library

In this project, you'll enhance the turtle drawing program by utilizing functions from Python's standard library.

import turtle
import random
import math
import datetime

# Create a new turtle screen and set its background color
screen = turtle.Screen()
screen.bgcolor("white")

# Initialize a turtle object
t = turtle.Turtle()

# Functions to draw shapes
def draw_square(side_length):
    for _ in range(4):
        t.forward(side_length)
        t.right(90)

def draw_circle(radius):
    t.circle(radius)

def draw_random_shape():
    shape_choice = random.choice(['square', 'circle'])
    if shape_choice == 'square':
        side_length = random.randint(50, 100)
        draw_square(side_length)
    else:
        radius = random.randint(50, 100)
        draw_circle(radius)

def print_date():
    current_date = datetime.date.today()
    print(f"Drawing created on {current_date}")

# Function to draw a pattern
def draw_pattern():
    for _ in range(36):
        draw_random_shape()
        t.right(10)
    print_date()

# Function to clear the screen
def clear_screen():
    t.clear()

# Bind the functions to keys
screen.onkey(draw_pattern, "p")
screen.onkey(clear_screen, "c")

# Start listening for key presses
screen.listen()

# Wait until the window is closed
turtle.done()

In this program, we've used the random module to choose between drawing a square or a circle and to determine their sizes. The datetime module is used to print the current date when the pattern is drawn.

The draw_pattern function draws a pattern of 36 random shapes, turning the turtle slightly after each shape to create a circular pattern. The user can press the "p" key to draw the pattern and the "c" key to clear the screen.

Try to modify this program to use more modules from the standard library, such as math for more complex calculations or json to save and load drawings.

In the next unit, we'll shift gears and explore working with APIs in Python, continuing to build on the foundational skills you've developed.