Lambda functions

Lambda functions are small, anonymous functions that can be defined in a simple one-line syntax, like so:

lambda arguments : expression

For example, take the following function that returns the sum of two values:

def add_up(x, y):
    return x + y
print(add_up(2, 5))
7

This function can equivalently be written using the lambda function syntax, as follows:

add_up = lambda x, y: x + y
print(add_up(2, 5))
7

Note that the main restriction of a lambda function is that it can only contain a single expression—that is, you need to be able to write the expression to return the value in a single line of code. This makes lambda functions convenient only in situations where the function is sufficiently simple such that it can be expressed in a single statement.

Exercise 56 – the first item in a list

In this exercise, you will write a lambda function, first_item, to select the first item in a list containing cat, dog, and...