Python Challenge of the Day (2/17/22)

Problem scenario
You have a program as follows:

class Location:
    def __init__(self, country="US", state="CA", city="Los Angeles"):
        self.country = country
        self.state = state
        self.city = city

    def printer(self):
        return [self.country, self.state, self.city]

new_loc = Location("Mexico", "Mexico City", "Mexico City", "good neighborhood")
print(new_loc.printer())

Here are your choices of what it could print out:

a. TypeError: init() takes from 1 to 4 positional arguments but 5 were given
b. TypeError: init() takes from 1 to 3 positional arguments but 4 were given
c. ['Mexico', 'Mexico City', 'Mexico City']
d. None of the above

Which one does it print?

Scroll down to see the answer.

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Answer
A. The reason is that the class methods always pass the self when there are stanzas like this:

new_loc = Location("Mexico", "Mexico City", "Mexico City", "good neighborhood")

The self is invisible, but behind-the-scenes, it is there.

It accepts four positional arguments: country, state, city, and self. The line causing the error includes "good neighborhood". To read more about this, see this StackOverflow posting.

The arity of the __init__ constructor (in the class Location) is variable -- but passing four arguments is excessive. It can handle three explicit parameters as "self" is passed implicitly. Python will print out "__init__() takes from 1 to 4 positional arguments but 5 were given"