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amandae
15,727 PointsUsing more than one default in Python Object parameters
When we open the workspace for this video, it has the following initalizer
def __init__(self, model, year, make='Ford', gas=100):
...
def __str__(self):
return f'{make} {model} {year}'
The instance is then defined as car_one = Car('Model T', 1908)
This returns the error
File "/home/treehouse/workspace/cars.py", line 72, in <module> print(car_one)
File "/home/treehouse/workspace/cars.py", line 19, in __str__ return f' {make} {model} {year}'
NameError: name 'make' is not defined
This makes it impossible to follow along in workspaces with the video.
And, while I'm on the topic, I have a related question. Yesterday I was trying out some code, and couldn't figure out how to use the first default and then change the second. For example, if I wanted the leave the make as Ford, but change the gas to 175. How does one do that?
Thank you!
3 Answers
Chris Freeman
Treehouse Moderator 68,441 PointsHey amandae, the issue is the variable names aren’t referencing the instance attributes.
self. prepended to them:
return f”{self.make} {self.model} {self.year}”
To change a default parameter include a keyword argument for that parameter. So the call now becomes:
car_one = Car('Model T', 1908, gas=175)
Post back if you need more help. Good luck!!!
amandae
15,727 PointsThanks. That does fix the problem in the example code. I'll send an email about that. Now that you say it, the fix seems so simple!
For the second part of the question, let me re-ask. I wasn't clear. I'm not trying to change the default, but change it from a default in an instance.
car_one = Car('Model T', 1908, ,175) <-- This doesn't work, and neither does undefined.
What needs to be in the "make" position in the instance to leave the default, but then change the next default?
Thank you!
Chris Freeman
Treehouse Moderator 68,441 PointsApologies, I was also unclear. I meant that the gas=175 was to be used in the calling arguments. I’ve updated my answer above.
amandae
15,727 PointsGot it! Thank you!
Chris Freeman
Treehouse Moderator 68,441 PointsChris Freeman
Treehouse Moderator 68,441 PointsWhen I load the video linked here and create a new workspace, the
__str__method includes the correctself.prefixes. Is it possible you are using a workspace from a different video? Maybe this video needs a “use new workspace” warning.