Can I have multiple constructors in python and overriding __str__ method

Question

done here, thank you! See answer in comments

Answer 1

Your code already meets the requirements: Act can be instantiated with 4 arguments, or with 3 arguments, in which case the stage is set to None. This use of optional parameters is good practice in python, but if you want to you can add a completely separate constructor implemented as a @classmethod as well:

class Act:
    def __init__(self, num_members, name, kind, stage):
        self._num_members = num_members
        self._name = name
        self._kind = kind
        self._stage = stage

    @classmethod
    def without_stage(cls, num_members, name, kind):
        return cls(num_members, name, kind, None)

Now you can instantiate Act as Act(num_members, name, kind, stage) or as Act.without_stage(num_members, name, kind).

Answer 2

Read more about having multiple constructors here: What is a clean, pythonic way to have multiple constructors in Python?

I was able to fix some issues in your code, please find them mentioned in my comments:

class Act:
    # works fine
    def __init__(self, num_members, name, kind, stage=None):
        self._num_numbers = num_members
        self._name = name
        self._kind = kind
        self._stage = stage

    # all the getters work fine
    def get_num_members(self):
        return self._num_numbers

    def get_name(self):
        return self._name

    def get_kind(self):
        return self._kind

    def get_stage(self):
        return self._stage

    # all the setters work fine now
    def set_num_members(self, num_numbers):
        self._num_numbers = num_numbers

    def set_name(self, name):
        self._name = name

    def set_kind(self, kind):
        self._kind = kind

    def set_stage(self, stage):
        self._stage = stage

    # I did not see the need for properties
    # def__str__(self): your code did not have a space here
    #    ^ here
    # "\n" is newline and not "/n"
    def __str__(self):
        string = "Number of members:" + str(self._num_numbers)
        string += "\nName: " + self._name
        string += "\nKind of act: " + self._kind
        if self._stage:
            string += "\nStage: " + self._stage
        return string

# create the object
a = Act("5", "h", "6", "7")
print(a)

Hope this helps. Good luck.