219 lines
3.6 KiB
Markdown
219 lines
3.6 KiB
Markdown
# Python Cheat Sheet
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## Table of Contents
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1. [Variables](#variables)
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2. [Data Types](#data-types)
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3. [Operators](#operators)
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4. [Control Structures](#control-structures)
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5. [Functions](#functions)
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6. [Lists](#lists)
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7. [Strings](#strings)
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8. [Dictionaries](#dictionaries)
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9. [Tuples](#tuples)
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10. [Sets](#sets)
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11. [File Handling](#file-handling)
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12. [Exception Handling](#exception-handling)
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13. [Classes and Objects](#classes-and-objects)
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## Variables
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### Declaration and Assignment
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```python
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variable_name = value
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```
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### Variable Types
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- String: `string_variable = "Hello"`
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- Integer: `int_variable = 42`
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- Float: `float_variable = 3.14`
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- Boolean: `bool_variable = True`
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## Data Types
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### Basic Types
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- String
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- Integer
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- Float
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- Boolean
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### Compound Types
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- List
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- Tuple
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- Set
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- Dictionary
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## Operators
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### Arithmetic Operators
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```python
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+, -, *, /, %, ** (exponentiation), //
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```
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### Comparison Operators
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```python
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==, !=, <, >, <=, >=
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```
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### Logical Operators
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```python
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and, or, not
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```
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### Assignment Operators
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```python
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=, +=, -=, *=, /=, %=
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```
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## Control Structures
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### If Statement
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```python
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if condition:
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# code to be executed if the condition is true
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elif another_condition:
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# code to be executed if the previous condition was false and this one is true
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else:
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# code to be executed if all conditions are false
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```
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### For Loop
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```python
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for i in range(5):
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# code to be executed in each iteration
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```
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### While Loop
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```python
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while condition:
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# code to be executed as long as the condition is true
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```
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## Functions
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### Function Declaration
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```python
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def function_name(param1, param2):
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# code to be executed
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return result # optional
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```
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### Function Call
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```python
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result = function_name(arg1, arg2)
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```
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## Lists
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### List Declaration
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```python
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my_list = [1, 2, 3, "hello", True]
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```
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### List Operations
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```python
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my_list.append(4) # Add an element to the end
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my_list.remove("hello") # Remove a specific element
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```
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## Strings
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### String Concatenation
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```python
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string1 = "Hello"
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string2 = "World"
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concatenated = string1 + " " + string2
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```
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### String Methods
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```python
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len(my_string) # Length of the string
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my_string.find("find") # Index of the first occurrence of "find"
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my_string.split(",") # Split the string into a list
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```
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## Dictionaries
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### Dictionary Declaration
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```python
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my_dict = {"key1": "value1", "key2": "value2"}
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```
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### Dictionary Operations
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```python
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my_dict["new_key"] = "new_value" # Add a new key-value pair
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del my_dict["key1"] # Remove a key-value pair
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```
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## Tuples
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### Tuple Declaration
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```python
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my_tuple = (1, 2, 3, "hello", True)
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```
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### Immutable Nature
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```python
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# Tuple elements cannot be changed once set
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my_tuple[0] = 4 # This will result in an error
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```
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## Sets
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### Set Declaration
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```python
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my_set = {1, 2, 3, 3, 4}
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```
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### Set Operations
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```python
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my_set.add(5) # Add an element to the set
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my_set.remove(3) # Remove an element from the set
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```
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## File Handling
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### Reading from a File
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```python
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with open("filename.txt", "r") as file:
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file_content = file.read()
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```
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### Writing to a File
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```python
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with open("filename.txt", "w") as file:
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file.write("Hello, World!")
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```
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## Exception Handling
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### Try-Except Block
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```python
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try:
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# code that may raise an exception
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except Exception as e:
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# handle the exception
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print("Error:", e)
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```
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## Classes and Objects
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### Class Declaration
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```python
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class MyClass:
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def __init__(self, name):
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self.name = name
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def say_hello(self):
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print(f"Hello, {self.name}!")
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```
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### Object Instantiation
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```python
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obj = MyClass("John")
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obj.say_hello() # Outputs: Hello, John!
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```
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```
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