CodeQL documentation

Non-iterable used in for loop

ID: py/non-iterable-in-for-loop
Kind: problem
Severity: error
Precision: high
Tags:
   - reliability
   - correctness
   - types
Query suites:
   - python-security-and-quality.qls

Click to see the query in the CodeQL repository

The for statement is designed to allow you to iterate over the elements of a sequence or other iterable object. If a non-iterable object is used in a for statement (for var in object:) then a TypeError will be raised.

Recommendation

Since this defect usually indicates a logical error, it is not possible to give a general method for addressing the defect.

Example

In this example, the loop may attempt to iterate over None, which is not an iterable. It is likely that the programmer forgot to test for None before the loop.



def illegal_for_loop(seq = None):
    for x in seq:
        print (x)

References