Non-callable called¶
ID: py/call-to-non-callable Kind: problem Security severity: Severity: error Precision: high Tags: - quality - reliability - correctness Query suites: - python-code-quality.qls - python-security-and-quality.qls Click to see the query in the CodeQL repository
If an object is called, obj(), then that object must be a callable or a TypeError will be raised. A callable object is any object whose class defines the __call__ special method. Callable objects include functions, methods, classes.
The callable(object) builtin function determines if an object is callable or not.
When the Python interpreter attempts to evaluate a call such as func(arg) it will invoke the __call__ special method on func. Thus, func(arg) is roughly equivalent to type(func).__call__(func, arg) which means that the class must define the attribute __call__, merely adding it to the instance is not sufficient.
Recommendation¶
Since this problem usually indicates a logical error, it is not possible to give a general recipe for fixing it.
Example¶
lists are not callable. In this example, an attempt is made to call a list which will fail with a TypeError.
a_list = [] a_list() References¶
Python Standard Library: callable.
Python Language Reference: object.call.