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‘super’ in old style class

ID: py/super-in-old-style
Kind: problem
Security severity: 
Severity: error
Precision: very-high
Tags:
   - portability
   - correctness
Query suites:
   - python-security-and-quality.qls

Click to see the query in the CodeQL repository

The ability to access inherited methods that have been overridden in a class using super() is supported only by new-style classes. When you use the super() function in an old-style class it fails.

Recommendation

If you want to access inherited methods using the super() built-in, then ensure that the class is a new-style class. You can convert an old-style class to a new-style class by inheriting from object. Alternatively, you can call the __init__ method of the superclass directly from an old-style class using: BaseClass.__init__(...).

Example

In the following example, PythonModule is an old-style class as it inherits from another old-style class. If the _ModuleIteratorHelper class cannot be converted into a new-style class, then the call to super() must be replaced. The PythonModule2 class demonstrates the correct way to call a superclass from an old-style class.

class PythonModule(_ModuleIteratorHelper): # '_ModuleIteratorHelper' and 'PythonModule' are old-style classes

    # class definitions ....

    def walkModules(self, importPackages=False):
        if importPackages and self.isPackage():
            self.load()
        return super(PythonModule, self).walkModules(importPackages=importPackages) # super() will fail


class PythonModule2(_ModuleIteratorHelper): # call to super replaced with direct call to class

    # class definitions ....

    def walkModules(self, importPackages=False):
        if importPackages and self.isPackage():
            self.load()
        return _ModuleIteratorHelper.__init__(PythonModule, self).walkModules(importPackages=importPackages)

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