learn-python-in-half-day-lesson-12.md

Lesson 12: Lambda Functions (10 minutes)

Welcome to Lesson 12! In this lesson, we'll explore lambda functions, a feature in Python that allows you to create small, anonymous functions. Lambda functions are useful for quick, one-line operations and can be used as arguments to higher-order functions.

Creating Lambda Functions:

In Python, lambda functions are defined using the lambda keyword, followed by the function's parameters and a single expression.

Example 1: Creating a Simple Lambda Function

# Regular function
def square(x):
    return x ** 2

# Equivalent lambda function
square_lambda = lambda x: x ** 2

Using Lambda Functions:

Lambda functions are often used as throwaway functions for short operations or as arguments to other functions like map(), filter(), and sorted().

Example 2: Using Lambda Functions with map()

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

# Using regular function with map()
squared = list(map(square, numbers))

# Using lambda function with map()
squared_lambda = list(map(lambda x: x ** 2, numbers))

Example 3: Using Lambda Functions with filter()

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

# Using regular function with filter()
even = list(filter(lambda x: x % 2 == 0, numbers))

Example 4: Using Lambda Functions with sorted()

words = ["apple", "banana", "orange", "grape"]

# Using regular function with sorted()
sorted_words = sorted(words, key=len)

# Using lambda function with sorted()
sorted_words_lambda = sorted(words, key=lambda word: len(word))

Key Differences for C# Developers:

• Lambda functions in Python are similar to C#'s lambda expressions, but in Python, they can be used more extensively with built-in functions like map(), filter(), and sorted().
• Python's lambda functions are limited to a single expression, while C#'s lambda expressions can contain multiple statements.

Now that you've learned about lambda functions in Python, you can use them to write more concise and expressive code for certain operations.

Additional Resources:

• Python Lambda Functions: https://docs.python.org/3/tutorial/controlflow.html#lambda-expressions

Practice Project:

• Write a Python script that takes a list of numbers as input and uses a lambda function with map() to calculate the square of each number and print the results.

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