What are lambda functions in Python?

Lambda functions in Python are small anonymous functions that are defined using the lambda keyword. Unlike regular functions that are defined with the def statement and require a name, lambda functions provide a way to create a function without explicitly naming it. They can take any number of arguments but can only have one expression, which is evaluated and returned when the function is called.

This feature makes lambda functions particularly useful for short, throwaway functions, especially in contexts where you need a simple function for a short period of time, such as when using functions like filter(), map(), or sorted(). For example, you might use a lambda function to specify a custom sorting key or to transform values in a list.

The other options do not accurately capture the essence of lambda functions. While there are predefined functions for mathematical calculations available in Python, these are not what lambda functions refer to. Lambda functions can indeed have a return value, as they evaluate the given expression, and they are capable of accepting multiple arguments, contrary to the suggestion that they can only take one argument.