class MyClass:
    def __init__(self, param1=None, param2=None):
        if param1 is not None and param2 is not None:
            # Constructor with both parameters
            self.param1 = param1
            self.param2 = param2
        elif param1 is not None:
            # Constructor with only param1
            self.param1 = param1
            self.param2 = "default_value_for_param2"
            # Default constructor with no parameters
            self.param1 = "default_value_for_param1"
            self.param2 = "default_value_for_param2"

    def display_params(self):
        print(f"param1: {self.param1}, param2: {self.param2}")

# Example usage
obj1 = MyClass()
obj1.display_params()  # Output: param1: default_value_for_param1, param2: default_value_for_param2

obj2 = MyClass("value1")
obj2.display_params()  # Output: param1: value1, param2: default_value_for_param2

obj3 = MyClass("value1", "value2")
obj3.display_params()  # Output: param1: value1, param2: value2