Pythonic Programming

Tip 60

Savvy Anonymous Functions

★★★^{2.7, 3.4+} In Python, you can have statements that do nothing (Tip 18, ​Pass It​) and variables never that get used (Tip 10, ​Mark Dummy Variables​). You can also have throw-away functions without names. They are known as anonymous functions or lambda functions.

A lambda function is a one-liner: a function that essentially consists of one statement. The value of the statement is the value returned by the function. If you need more than one statement, a lambda function is not going to help.

A lambda function does not have a name. You create it as needed with the lambda keyword, use it at once, and discard it. Here is a lambda function that squares its parameter:

z = (lambda x: x * x)(3)

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And this ...