How To Use Yield in Python To Make Your Functions More Efficient

Use yield to turn your functions into memory-efficient generators

Photo by Chris Ried on Unsplash.

In Python, yield is used to return from a function without destroying its variables. In a sense, yield pauses the execution of the function. When the function is invoked again, the execution continues from the last yield statement.

Using yield turns a function into a generator. Here is an illustration of functions vs. generators:

Image by the author.

A generator returns a generator object, also known as an iterator, that generates one value at a time. It does not store any values. This makes a generator memory-efficient.

For example, you can use a generator to loop through a group of numbers without storing any of them in memory.

How To Turn a Function Into a Generator

To turn a function into a generator, yield a value instead of returning it. This makes the function return a generator object. This is an iterator you can loop through like a list.

Example

Let’s create a square() function that squares an input list of numbers:

Output:

[1, 4, 9, 16, 25]

Let’s turn this function into a generator. Instead of storing the squared numbers into a list, you can yield values one at a time without storing them:

Output:

<generator object square at 0x7f685175b510>