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.

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

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.

Python Language Reference: The for statement, object.__iter__.

Python Standard Library: Iterator types.

Scipy lecture notes: Iterators, generator expressions and generators.