class - member variable string gets treated as Tuple in Python

Question

I am currently learning Python with the help of CodeAcademy. My problem may be related to their web application, but my suspicion is I am just wrong on a very fundamental level here.

If you want to follow along I am referring to CodeAcademy.com -> Python -> Classes 6/11

My code looks like this:

class Car(object):
    condition = "new"
    def __init__(self, model, color, mpg):
        self.model = model,
        self.color = color,
        self.mpg = mpg

my_car = Car("DeLorean", "silver", 88)
print my_car.model
print my_car.color
print my_car.mpg
print my_car.condition

What is suppossed to happen, is, that every member variable of the object my_car gets printed on screen. I was expecting that like condition, color and model would be treated as a string, but instead get treated as a Tuple.

The output looks like this:

('DeLorean',) #Tuple
('silver',) #Tuple
88 
new #String
None

Which leads to the validation failing, because CA expects "silver" but the code returns ('silver',).

Where is the error in my code on this?

I'm grateful for your question. I teach Python, and the trailing comma issue. This is the first time I have come across a real live example of someone making this mistake! Thanks. — cdarke
Aye, it is very hard, to unlearn everything one does know about other languages. Every so often I write object = new class just because I am used to it. I guess I will be stumbling about syntactical mashups very often the upcoming weeks. — Marco

fredtantini fredtantini · Accepted Answer · 2014-12-26T08:27:10

In your __init__, you have:

    self.model = model,
    self.color = color,

which is how you define a tuple. Change the lines to

    self.model = model
    self.color = color

without the comma:

>>> a = 2,
>>> a
(2,)

vs

>>> a = 2
>>> a
2

class - member variable string gets treated as Tuple in Python

3 Answers