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Use of ‘return’ or ‘yield’ outside a function

ID: py/return-or-yield-outside-function
Kind: problem
Security severity: 
Severity: error
Precision: medium
Tags:
   - reliability
   - correctness
Query suites:
   - python-security-and-quality.qls

Click to see the query in the CodeQL repository

In Python, return and yield statements and the yield from expression can only be used within a function. Using them outside a function or a class method results in a SyntaxError at runtime.

Recommendation

Using these elements outside a function or a class method usually indicates an error in the logic. Consequently, it is not possible to suggest a general fix.

Example

In this example, a return statement is used outside a class method in a class and a yield statement is used outside a function in a scope of a module which would result in a SyntaxError when running this code. In this example, the invalid class could be corrected by placing the return statement in a class method, or by refactoring the class into a function. The invalid yield statement could become part of a new generator function containing the for loop.

# invalid class with return outside a function
class InvalidClass1(object):
    if [1, 2, 3]:
        return "Exists"

# invalid statement with yield outside a function
for i in [1, 2, 3]:
    yield i

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