Python Cheat Sheet

1. Variables, Data Types, and Basic Operations

Python has several fundamental data types, including integers (int), floating point numbers (float), and strings (str). Python is a dynamically typed language, which means you don't need to declare the data type of a variable when you define it.

a = 10  # Integer
b = 3.14  # Float
c = "Hello, World!"  # String

Operators allow you to perform operations on variables. Arithmetic, comparison, assignment, logical, and identity operators are some of the main types in Python.

a = 10
b = 20
sum = a + b  # Addition
difference = a - b  # Subtraction
#... remaining code ...

2. Control Structures (Conditionals and Loops)

Python uses if, elif, and else for conditional statements. Loops in Python can be programmed using a for or while loop.

# If-else statement
if a > b:
    print("a is greater than b")
else:
    print("a is not greater than b")

# For loop
for i in range(5):
    print(i)

3. Functions

Functions in Python are defined using the def keyword. They are used to encapsulate a piece of code that performs a specific task.

def greet(name):
    print("Hello, " + name)

greet("Alice")

4. Lists, Tuples, Sets, and Dictionaries

Python has several types of compound data structures that can hold multiple values, including lists, tuples, sets, and dictionaries.

# Lists
my_list = [1, 2, 3, 4, 5]

# Dictionaries
my_dict = {"apple": 1, "banana": 2, "cherry": 3}

5. File Handling

Python has built-in functions for reading and writing files. open() function is used to open a file. It returns a file object and is most commonly used with two arguments: open(filename, mode).

# Reading a file
file = open('file.txt', 'r')
content = file.read()
file.close()

# Writing to a file
file = open('file.txt', 'w')
file.write("Hello, World!")
file.close()

6. Exception Handling

Python uses try and except blocks to catch and handle exceptions. Python executes code following the try statement as a "normal" part of the program. The code that follows the except statement is the program's response to any exceptions in the preceding try clause.

try:
    # Code that may raise an exception
    x = 1 / 0
except ZeroDivisionError:
    print("You can't divide by zero!")

7. Classes and Objects

Python is an object-oriented programming language. You define classes to create your own types.

class MyClass:
    x = 5

p1 = MyClass()  # Create an object of MyClass
print(p1.x)  # Access the properties of MyClass using the object

8. Modules and Packages

Modules in Python are simply Python files with a .py extension, which implement a set of functions. A package is a way of organizing related modules into a single directory hierarchy.

# Importing a module
import math
print(math.sqrt(16))  # Use a function from the math module

# Importing
ChatGPT
 a package
import os.path
print(os.path.join('/a', 'b', 'c'))  # Use a function from the os.path package

9. Working with JSON

Python has a built-in package called json, which can be used to work with JSON data.

import json

# Some JSON:
x = '{"name": "John", "age": 30, "city": "New York"}'

# Parse x:
y = json.loads(x)

# The result is a Python dictionary:
print(y["age"])

10. Making HTTP requests

The requests library is the de facto standard for making HTTP requests in Python. It abstracts the complexities of making requests behind a beautiful, simple API so that you can focus on interacting with services and consuming data in your application.

import requests

response = requests.get('https://www.example.com')

# Print the status code
print(response.status_code)

# Print the content
print(response.text)

These are the basics to get you started with Python! Each of these topics has more depth to explore as you become more comfortable with the language.

3.9 KiB Raw Blame History