Python Functions with some tricks

Tuesday. July 25, 2017 - 1 min

Define functions is one of basic Python skills. I would like to focus on closure and its tricks.

Metadata

We can add some annotations on function in order to let programmers know how this function should be used.

Python interpreter wouldn’t give any semantic meaning on these statement. They are not type checks mechanism. However, they still give other maintainers enough clues to track code.

If functions have multiple values to return, they are packed in tuple and returned.

Default value in parameters

Indicated default values should always be immutable objects Like None, True, False, number or string

Capture variable in lambda

Using functools.partial

Closure

When do we have a closure?

We must have a nested function (function inside a function).
The nested function must refer to a value defined in the enclosing function.
The enclosing function must return the nested function.

When to use closures?

Closures can avoid the use of global values and provides some form of data hiding. It can also provide an object oriented solution to the problem.

We may want to replace single-method class with closure.

We may also want our callback functions to bring additional information

Reference

[1] Python Closures [2] Python cookbook 3rd version

Vic Yang

Back-end Engineer