Magic Methods in Python can be Risky

This code insight counts one violation each time a magic method is called, except if it is in the body of a magic method.

bad

first_names = ["eve", "lisa", "robert", "paul", "alice"]
if first_names.__contains__("robert"):
    print("list of first names contains robert")

good

example 1

first_names = ["eve", "lisa", "robert", "paul", "alice"]
if "robert" in first_names:
    print("list of first names contains robert")

this example illustrate the work around for the bad example above: the __contains__ method is still called, but in background through the use of python high level mechanism, for which magic methods are intended to be used.

example 2

class child_class(parent_class):
def __init__():
super().__init__()

def __contains__(arg1, arg2):
parent_class.__contains__(arg1)
print(arg2)

in this example, the call to super().__init__() and parent_class.__init__() are not violation because its a call of parent’s method in a context of respectively overriding and overloading