Yield

The yield statement suspends a function's execution and sends a value back to the caller.

Yield retains enough state to enable the function to resume where it left off.

When the function resumes, it continues execution immediately after the last yield run.

This allows its code to produce a series of values over time, rather than computing them at once and sending them back like a list.

def simpleGeneratorFun():
    yield 1
    yield 2
    yield 3

for value in simpleGeneratorFun():
    print(value) # 1 2 3

Useful when streaming data to client:

from django.http import StreamingHttpResponse

def streaming_data():
    # simulate a streaming of data
    for i in range(10):
        # yielding a chunked stream data
        yield f"data: {i}\n\n"

response = StreamingHttpResponse(streaming_data(), content_type="text/event-stream")

return response

return vs yield

Return sends a specified value back to its caller.

Yield can produce a sequence of values.

Use yield when we want to iterate over a sequence, but don't want to store the entire sequence in memory.