Lambda functions#

In Python, a lambda function is an anonymous function, that is, a function that is declared without a name. It is a small and restricted function that is no longer than one line. Like a normal function, a lambda function can have several arguments, but only one expression that is evaluated and returned.

The syntax of a lambda function is


>>> add = lambda x, y: x + y
>>> add(2, 3)


There is no return statement in the lambda function. The single expression after the colon is the return value.

In the next example, a lambda function is created within a function call. However, there is no global variable to store the values of the lambda function:

1>>> count = ['1', '123', '1000']
2>>> max(count)
4>>> max(count, key=lambda val: int(val))

In this case, the max() function accepts the key argument, which defines how the size of each entry is to be determined. Using a lambda function that converts each string into an integer, max can compare the numerical values to determine the expected result.