lambda functions, enumeratem, zip, map, filter

Here’s an easy-to-understand guide to lambda, functions, enumerate, zip, map, filter in Python 🐍✨—with emojis, explanations, code examples, and practice questions!

🔹 lambda (Anonymous Functions)

• lambda creates small, unnamed functions on the fly.
• Syntax: lambda arguments: expression
• Useful for short, simple functions, especially as arguments to other functions.

# Example: square of a number
square = lambda x: x * x
print(square(5))  # 25

# Example with two arguments
add = lambda x, y: x + y
print(add(3, 4))  # 7

You can assign a lambda to a variable or use it directly!

🔹 Functions

• Defined using def.
• Can have parameters and return values.

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

print(greet("Alice"))  # Hello, Alice!

Functions organize code and make it reusable.

🔹 enumerate

• Adds a counter to an iterable (like a list or string).
• Returns pairs of (index, item).

fruits = ['apple', 'banana', 'cherry']
for idx, fruit in enumerate(fruits):
    print(idx, fruit)
# Output:
# 0 apple
# 1 banana
# 2 cherry

Great for when you need both the item and its position! ¹²

🔹 zip

• Combines multiple iterables into tuples, stopping at the shortest.
• Useful for parallel iteration.

names = ['Anil', 'Bina', 'Chetan']
marks = [85, 92, 78]
for name, mark in zip(names, marks):
    print(name, mark)
# Output:
# Anil 85
# Bina 92
# Chetan 78

You can use list(zip(...)) to see all pairs at once. ¹²

🔹 map

• Applies a function to every item in an iterable.
• Returns an iterator (use list() to get all results).

nums = [1, 2, 3, 4]
squares = list(map(lambda x: x*x, nums))
print(squares)  # [1, 4, 9, 16]

map is often used with lambda for concise code! ¹²

🔹 filter

• Filters items in an iterable by a function that returns True/False.
• Returns an iterator (use list() to get all results).

nums = [1, 2, 3, 4, 5, 6]
evens = list(filter(lambda x: x % 2 == 0, nums))
print(evens)  # [2, 4, 6]

filter is great for extracting items that meet a condition! ¹²

🏋️‍♂️ Practice Questions

1️⃣ Use map to add 10 to every number in [^1][^2][^3].

nums = [1, 2, 3]
result = list(map(lambda x: x + 10, nums))
print(result)  # [11, 12, 13]

2️⃣ Use filter to keep only words longer than 3 letters in ['cat', 'lion', 'tiger'].

words = ['cat', 'lion', 'tiger']
result = list(filter(lambda w: len(w) > 3, words))
print(result)  # ['lion', 'tiger']

3️⃣ Use enumerate to print the index and value of each character in “dog”.

for idx, char in enumerate("dog"):
    print(idx, char)
# Output:
# 0 d
# 1 o
# 2 g

4️⃣ Use zip to pair elements from [^1][^2][^3] and ['a', 'b', 'c'].

nums = [1, 2, 3]
letters = ['a', 'b', 'c']
pairs = list(zip(nums, letters))
print(pairs)  # [(1, 'a'), (2, 'b'), (3, 'c')]

⭐ Key Points Table

Practice these tools—they make your Python code powerful and concise! 🚀 If you want more examples or have questions, just ask!