152 lines
3.9 KiB
Markdown
152 lines
3.9 KiB
Markdown
# 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.
|
|
|
|
```python
|
|
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.
|
|
|
|
```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.
|
|
|
|
```python
|
|
# 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.
|
|
|
|
```python
|
|
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.
|
|
|
|
```python
|
|
# 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)`.
|
|
|
|
```python
|
|
# 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.
|
|
|
|
```python
|
|
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.
|
|
|
|
```python
|
|
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.
|
|
|
|
```python
|
|
# 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.
|
|
|
|
```python
|
|
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.
|
|
|
|
```python
|
|
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.
|