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Python Object-Oriented Python Instant Objects Master Class

Posted by Marco Koopman
Marco Koopman
5,290 Points

How to global scope a var in a class

Hey!

I'm wondering how you can make a variable global ( so that I don't have to use 'self').

Normally it works to define it right under the class and above the constructor but in Python this gives me a scoping error.

racecar.py 
class RaceCar:

    laps = 0

    def __init__(self, color, fuel_remaining, **kwargs):

        self.color = color
        self.fuel_remaining = fuel_remaining

        for key, value in kwargs.items():

            setattr(self, key, value)

    def run_lap(length):
        laps += 1
        self.fuel_remaining = self.length * 0.125

2 Answers

Dave StSomeWhere
Dave StSomeWhere
19,870 Points
Dave StSomeWhere
Dave StSomeWhere
19,870 Points

I think your issue is that you are missing self in your run_lap() method def - not any issue with scoping.

The scoping seems fine (as you described) if the following code is what you meant:

class RaceCar:

    test_var = "hello Race Car"
    test2 = "Gonna assign to instance"

    def __init__(self, color, fuel_remaining, **kwargs):
        self.laps = 0
        self.color = color
        self.fuel_remaining = fuel_remaining
        for key, value in kwargs.items():
            setattr(self, key, value)

    def run_lap(self, length):
        self.fuel_remaining -= length * 0.125
        self.laps += 1
        test_var = "changed in runlap"
        self.test2 = "Assigned to Instance***"
        print("test_var in runlap ==> " + test_var)
        print("self.test2 in runlap ==> " + self.test2)

a = RaceCar("Blue", 100)
a.run_lap(25)
print("fuel remaining ==> " + str(a.fuel_remaining))
print("test var ===> " + a.test_var)
print("test2 ===> " + a.test2)
Marco Koopman
Marco Koopman
5,290 Points

Hey! Thanks for the reply. I already fixed the missing self parameter but I still get an error saying the variable 'laps' is referenced before assignment

Dave StSomeWhere
Dave StSomeWhere
19,870 Points
Dave StSomeWhere
Dave StSomeWhere
19,870 Points

Yes, I see what you are talking about - laps doesn't exist without any reference. It need to be either self.laps for the instance or RaceCar.laps for the class. Just laps doesn't exist and attempting laps += 1 results in an error within the method.

Marco Koopman
Marco Koopman
5,290 Points
Marco Koopman
Marco Koopman
5,290 Points

Hey!

I've ajusted the code and it doesn't give any errors anymore. However the fuel_remaining variable isn't changing. I really don't understand how this scoping works.

class RaceCar:

laps = 0

def __init__(self, color, fuel_remaining, **kwargs):
    self.color = color
    self.fuel_remaining = fuel_remaining

    for key, value in kwargs.items():

        setattr(self, key, value)

def run_lap(self, length):
    RaceCar.laps += 1
    self.fuel_remaining = length * 0.125
    print(self.fuel_remaining)