How to Use yield in Python: Simple Guide with Examples

In Python, yield is used inside a function to make it a generator that produces values one at a time, pausing after each yield and resuming on the next call. This helps save memory and allows iteration over large or infinite sequences without creating them all at once.

Syntax

The yield keyword is used inside a function to return a value and pause the function's execution. When the function is called again, it resumes right after the yield. This makes the function a generator.

• def function_name(): defines the generator function.
• yield value returns a value and pauses.
• The function returns a generator object when called.

python

def simple_generator():
    yield 1
    yield 2
    yield 3

Example

This example shows a generator function that yields numbers from 1 to 3. Each time we loop over it, it produces the next number without storing all numbers at once.

python

def count_up_to_three():
    yield 1
    yield 2
    yield 3

for number in count_up_to_three():
    print(number)

Output

1
2
3

Common Pitfalls

One common mistake is expecting a generator function to return a list or all values at once. Instead, it returns a generator object that produces values on demand. Another mistake is forgetting to use yield and using return inside the generator, which stops the function immediately.

python

def wrong_generator():
    return 1  # This stops the function immediately
    yield 2

def correct_generator():
    yield 1
    yield 2

print(list(correct_generator()))  # Correct way to get all values

# Output:
# [1, 2]

Output

[1, 2]

Quick Reference

Concept	Description
yield	Pauses function and returns a value, making it a generator
Generator function	A function with at least one yield statement
Generator object	Returned when calling a generator function; produces values on demand
Iteration	Use a for loop or next() to get values from a generator
Memory efficiency	Generators produce values one at a time, saving memory

Key Takeaways

Use yield inside a function to create a generator that produces values lazily.

Generator functions return a generator object, not a list of values.

Each yield pauses the function and resumes on the next call.

Generators save memory by producing one value at a time instead of all at once.

Avoid using return to send values inside generators; use yield instead.