Python Cheatsheet

• Variables: Variables do not need explicit declaration.

```python

  x = 5
  name = "John"
  ```

• Comments:

```python

  # This is a single-line comment

  """
  This is a
  multi-line comment
  """
  ```

• Common Types:
  • int: `x = 10`
  • float: `y = 3.14`
  • str: `text = “Hello”`
  • list: `lst = [1, 2, 3]`
  • tuple: `tup = (1, 2, 3)`
  • dict: `d = {“key”: “value”}`
  • bool: `flag = True`

• If-else statement:

```python

  if x > 5:
      print("x is greater than 5")
  elif x == 5:
      print("x is 5")
  else:
      print("x is less than 5")
  ```

• Loops:
  • For loop:

```python

    for i in range(5):
        print(i)
    ```

• While loop:

```python

    count = 0
    while count < 5:
        print(count)
        count += 1
    ```

• Defining a function:

```python

  def greet(name):
      return f"Hello, {name}"
  ```

• Lambda Functions:

```python

  add = lambda x, y: x + y
  print(add(2, 3))
  ```

• List methods:

```python

  lst = [1, 2, 3]
  lst.append(4)
  lst.remove(2)
  print(lst)
  ```

• Dictionary methods:

```python

  d = {"name": "Alice", "age": 25}
  print(d["name"])
  d["age"] = 26
  ```

• Try-Except Block:

```python

  try:
      result = 10 / 0
  except ZeroDivisionError:
      print("Cannot divide by zero")
  finally:
      print("End of try-except block")
  ```

• Reading a file:

```python

  with open("file.txt", "r") as file:
      content = file.read()
  print(content)
  ```

• Writing to a file:

```python

  with open("file.txt", "w") as file:
      file.write("Hello, World!")
  ```

• Importing a module:

```python

  import math
  print(math.sqrt(16))
  ```

• Custom module:

```python

  # In mymodule.py
  def add(x, y):
      return x + y

  # In main file
  from mymodule import add
  print(add(3, 4))
  ```

• Defining a class:

```python

  class Person:
      def __init__(self, name, age):
          self.name = name
          self.age = age

      def greet(self):
          print(f"Hello, my name is {self.name}")

  p = Person("Alice", 25)
  p.greet()
  ```

• Range: `range(5)` generates numbers 0 to 4.
• Len: `len(lst)` returns the length of a list.
• Type: `type(x)` returns the data type of `x`.
• Input: `input(“Enter your name: ”)` takes user input.

• List comprehensions:

```python

  squares = [x**2 for x in range(5)]
  print(squares)
  ```

• Unpacking:

```python

  a, b = 1, 2
  print(a, b)
  ```

This cheatsheet covers the basics of Python syntax and essential concepts for quick reference. For more details, refer to the official Python documentation.