__call__ is also used to implement decorator classes in python. In this case the instance of the class is called when the method with the decorator is called.
class EnterExitParam(object):
def __init__(self, p1):
self.p1 = p1
def __call__(self, f):
def new_f():
print("Entering", f.__name__)
print("p1=", self.p1)
f()
print("Leaving", f.__name__)
return new_f
@EnterExitParam("foo bar")
def hello():
print("Hello")
if __name__ == "__main__":
hello()
program output:
Entering hello
p1= foo bar
Hello
Leaving hello