What is a lambda function in Python?

A **lambda function** in Python is a small anonymous function defined using the `lambda` keyword. Unlike regular functions defined with `def`, lambda functions are typically used for short, simple operations and are often written in a single line. The basic syntax is: ```python lambda arguments: expression ``` The expression is evaluated and returned when the lambda function is called. For example: ```python square = lambda x: x * x print(square(5)) # Output: 25 ``` Here, `square` is a lambda function that takes one argument `x` and returns its square. ### How to Use Lambda Functions Effectively 1. **Use for short, simple functions:** Lambda functions are ideal when you need a quick function for a short period, especially when passing functions as arguments. 2. **Common use cases include:** - **Sorting:** Using `key` parameter with `sorted()`, `list.sort()`, or `max()/min()`. ```python points = [(2, 3), (1, 4), (4, 1)] points_sorted = sorted(points, key=lambda point: point[1]) print(points_sorted) # Output: [(4, 1), (2, 3), (1, 4)] ``` - **Functional programming tools:** such as `map()`, `filter()`, and `reduce()`. ```python numbers = [1, 2, 3, 4] squared = list(map(lambda x: x**2, numbers)) print(squared) # Output: [1, 4, 9, 16] ``` 3. **Keep them simple:** Since lambda functions can only contain expressions (not statements), they are best suited for simple operations. If your logic grows complex, it’s better to define a named function with `def` for clarity and maintainability. 4. **Avoid overusing:** While convenient, overusing lambda functions, especially with complex expressions, can reduce code readability. In summary, lambda functions provide a concise way to write small, throwaway functions and are particularly useful in functional programming patterns or when needing a quick function for a short task.