What does __contains__ do, what can call __contains__ function

Question

Here is my code:

class a(object):
    d=\'ffffd\'
    def __contains__(self):
        if self.d:return True
b=a()
print b.contains(\'d\')  # error
print contai         


        

Answer 1

__contains__ method defines how instances of class behave when they appear at right side of in and not in operator.

class Person(object):
      def __init__(self,name,age):
          self.name = name
          self.age = age
      def __contains__(self,param1):
          return True if param1 in self.__dict__.keys() else False

>>> p = Person('Robby Krieger',23)
>>> 'name' in p
True