Collect 200 Python tricks

1. Basic Tricks

• Swapping Variables: a, b = b, a

• Multiple Assignment: a, b, c = 1, 2, 3

• Unpacking Lists/Tuples: a, *b, c = [1, 2, 3, 4]

• Inline If-Else: result = a if condition else b

• String Reversal: reversed_string = my_string[::-1]

2. List and Dictionary Comprehensions

• Simple List Comprehension: [x**2 for x in range(10)]

• Filtering with List Comprehension: [x for x in range(10) if x % 2 == 0]

• Nested Comprehensions: matrix = [[i for i in range(5)] for _ in range(3)]

• Dictionary Comprehension: {i: i**2 for i in range(5)}

• Set Comprehension: {i for i in range(10) if i % 2 == 0}

3. Lambda Functions

• Basic Lambda: add = lambda x, y: x + y

• Sorting with Lambda: sorted_list = sorted(my_list, key=lambda x: x[1])

• Filtering with Lambda: filtered = filter(lambda x: x % 2 == 0, my_list)

• Mapping with Lambda: mapped = map(lambda x: x * 2, my_list)

4. Advanced Data Structures

• Default Dictionary:

  pythonCopy codefrom collections import defaultdict
  d = defaultdict(int)
  d['key'] += 1

• Counter:

  pythonCopy codefrom collections import Counter
  count = Counter(my_list)

• Named Tuples:

  pythonCopy codefrom collections import namedtuple
  Point = namedtuple('Point', ['x', 'y'])
  p = Point(1, 2)

• Deque for Efficient Queues:

  pythonCopy codefrom collections import deque
  d = deque()
  d.append('task')
  d.popleft()

5. File Handling

• Context Manager:

  pythonCopy codewith open('file.txt', 'r') as f:
      data = f.read()

• Reading a File Line by Line:

  pythonCopy codewith open('file.txt', 'r') as f:
      for line in f:
          print(line.strip())

• Writing to a File:

  pythonCopy codewith open('file.txt', 'w') as f:
      f.write('Hello, World!')

6. Pythonic Code Practices

• Enumerate:

  pythonCopy codefor index, value in enumerate(my_list):
      print(index, value)

• Zip to Iterate in Parallel:

  pythonCopy codefor x, y in zip(list1, list2):
      print(x, y)

• List Flattening:

  pythonCopy codeflat_list = [item for sublist in my_list for item in sublist]

• Using _ for Ignoring Values:

  pythonCopy codefor _ in range(5):
      print("Hello")

7. Error Handling

• Basic Try-Except:

  pythonCopy codetry:
      result = 10 / 0
  except ZeroDivisionError:
      print("You can't divide by zero!")

• Finally Clause:

  pythonCopy codetry:
      f = open('file.txt', 'r')
  except FileNotFoundError:
      print('File not found')
  finally:
      f.close()

• Else in Try-Except:

  pythonCopy codetry:
      result = 10 / 2
  except ZeroDivisionError:
      print("You can't divide by zero!")
  else:
      print("Result is:", result)

8. Working with Modules

• Importing Modules:

  pythonCopy codeimport math
  from math import sqrt

• Importing with Aliases:

  pythonCopy codeimport numpy as np

• Reloading Modules (for development):

  pythonCopy codeimport importlib
  importlib.reload(module)

9. Function Tricks

• Default Arguments:

  pythonCopy codedef greet(name="World"):
      print(f"Hello, {name}")

• Arbitrary Arguments:

  pythonCopy codedef foo(*args, **kwargs):
      print(args)
      print(kwargs)

• Functions as First-Class Citizens:

  pythonCopy codedef add(x, y):
      return x + y
  
  operations = [add, lambda x, y: x * y]

• Recursive Functions:

  pythonCopy codedef factorial(n):
      return 1 if n == 0 else n * factorial(n - 1)

10. Decorators

• Basic Decorator:

  pythonCopy codedef my_decorator(func):
      def wrapper():
          print("Something before the function")
          func()
          print("Something after the function")
      return wrapper
  
  @my_decorator
  def say_hello():
      print("Hello!")

• Decorator with Arguments:

  pythonCopy codedef repeat(num_times):
      def decorator(func):
          def wrapper(*args, **kwargs):
              for _ in range(num_times):
                  func(*args, **kwargs)
          return wrapper
      return decorator
  
  @repeat(3)
  def greet(name):
      print(f"Hello, {name}")

11. Generators

• Basic Generator:

  pythonCopy codedef my_generator():
      yield 1
      yield 2
      yield 3
  
  for value in my_generator():
      print(value)

• Generator Expressions:

  pythonCopy codesquares = (x**2 for x in range(10))
  for square in squares:
      print(square)

12. Handling Time and Date

• Current Date and Time:

  pythonCopy codefrom datetime import datetime
  now = datetime.now()

• Time Delta:

  pythonCopy codefrom datetime import timedelta
  yesterday = datetime.now() - timedelta(days=1)

• Formatting Date and Time:

  pythonCopy codenow.strftime("%Y-%m-%d %H:%M:%S")

• Parsing Date Strings:

  pythonCopy codedatetime.strptime('2024-08-14', '%Y-%m-%d')

13. Useful Built-in Functions

• All and Any:

  pythonCopy codeall([True, True, False])  # False
  any([True, True, False])  # True

• Sum of Elements:

  pythonCopy codesum([1, 2, 3, 4])

• Max and Min:

  pythonCopy codemax([1, 2, 3, 4])
  min([1, 2, 3, 4])

• Reversing an Iterable:

  pythonCopy codelist(reversed([1, 2, 3, 4]))

14. Working with JSON

• Loading JSON:

  pythonCopy codeimport json
  data = json.loads('{"key": "value"}')

• Dumping JSON:

  pythonCopy codejson_string = json.dumps(data)

• Pretty Printing JSON:

  pythonCopy codeprint(json.dumps(data, indent=4))

15. Object-Oriented Programming

• Basic Class Definition:

  pythonCopy codeclass Dog:
      def __init__(self, name):
          self.name = name
      
      def bark(self):
          print(f"{self.name} says woof!")

• Inheritance:

  pythonCopy codeclass Animal:
      def speak(self):
          pass
  
  class Dog(Animal):
      def speak(self):
          return "Woof!"

• Class and Static Methods:

  pythonCopy codeclass MyClass:
      @classmethod
      def class_method(cls):
          print("Class method called")
      
      @staticmethod
      def static_method():
          print("Static method called")

16. Miscellaneous

• Ternary Operators:

  pythonCopy codeis_even = "Yes" if x % 2 == 0 else "No"

• Chaining Comparisons:

  pythonCopy codea = 5
  if 1 < a <