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yield-in-for-loop (UP028)

Added in v0.0.210 · Related issues · View source

Derived from the pyupgrade linter.

Fix is sometimes available.

What it does

Checks for for loops that can be replaced with yield from expressions.

Why is this bad?

If a for loop only contains a yield statement, it can be replaced with a yield from expression, which is more concise and idiomatic.

Example

def bar():
    for x in foo:
        yield x

    global y
    for y in foo:
        yield y

Use instead:

def bar():
    yield from foo

    for _element in foo:
        y = _element
        yield y

Fix safety

This rule's fix is marked as unsafe, as converting a for loop to a yield from expression can change the behavior of the program in rare cases. For example, if a generator is being sent values via send, then rewriting to a yield from could lead to an attribute error if the underlying generator does not implement the send method.

Additionally, if at least one target is global or nonlocal, no fix will be offered.

In most cases, however, the fix is safe, and such a modification should have no effect on the behavior of the program.

References