🚀 Lambda Functions — Quick, One-Line Functions

Lambda functions are small, unnamed functions you can write in one line. Perfect for quick operations.

🎯 What's a Lambda?

A lambda is a small, unnamed function you can write in one line without using the `def` keyword. It's perfect for tiny operations where a full function definition would be overkill. Lambda functions are especially useful when you need a function just for one quick use, like inside a `map()` or `filter()` call.

# Regular function
def add(a, b):
    return a + b

# Lambda function (same thing, one line)
add_lambda = lambda a, b: a + b

print(add(5, 3))        # Output: 8
print(add_lambda(5, 3)) # Output: 8

💡 Simple Examples

# Square a number
square = lambda x: x ** 2
print(square(5))  # Output: 25

# Check if number is even
is_even = lambda x: x % 2 == 0
print(is_even(4))  # Output: True
print(is_even(7))  # Output: False

🎨 Using Lambda with map()

The `map()` function is perfect for transforming data. It takes a function and applies it to every item in a list, creating a new list with the transformed values. Lambda is ideal here because you can define your transformation inline without needing a separate function definition. It's a clean, readable way to modify all items in a collection at once.

numbers = [1, 2, 3, 4, 5]

# Double every number
doubled = list(map(lambda x: x * 2, numbers))
print(doubled)  # [2, 4, 6, 8, 10]

# Square every number
squared = list(map(lambda x: x ** 2, numbers))
print(squared)  # [1, 4, 9, 16, 25]

🔍 Using Lambda with filter()

The `filter()` function lets you select only the items from a list that meet a certain condition. Your lambda function returns `True` or `False` for each item, and `filter()` keeps only the items where it's `True`. This is a powerful way to clean, organize, or extract specific data from a collection without writing a loop manually.

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

# Keep only even numbers
evens = list(filter(lambda x: x % 2 == 0, numbers))
print(evens)  # [2, 4, 6, 8, 10]

# Keep only numbers > 5
big = list(filter(lambda x: x > 5, numbers))
print(big)  # [6, 7, 8, 9, 10]

✅ When to Use Lambda

Use lambda when:

• You need a quick function

• The function is simple (1-2 lines)

• You're using it with map() or filter()

Don't use lambda when:

• The function is complex

• You'll use it many times (define a regular function instead)

🔑 Key Takeaways

🔗 What's Next?

Now let's explore decorators — functions that enhance other functions!

Next: Decorators →

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