Python: Essential Reference, Third Edition

The lambda Operator

To create an anonymous function in the form of an expression, use the lambda statement:

lambda args : expression

args is a comma-separated list of arguments, and expression is an expression involving those arguments. For example:

a = lambda x,y : x+y
print a(2,3)              # produces 5

The code defined with lambda must be a valid expression. Multiple statements and other non-expression statements, such as print, for, and while, cannot appear in a lambda statement. lambda expressions follow the same scoping rules as functions.