Learning python I was rewriting some of my old programs to see the
pros and cons of python when a steped in some weird (at least for me)
behavior.
Here it is simplified
The code:
>>> class Test1:
myList = [4 for n in range(4)]
myInt = 4
>>> a = Test1()
>>> b = Test1()
>>> a.myList
[4, 4, 4, 4]
>>> a.myInt
4
>>> b.myList
[4, 4, 4, 4]
>>> b.myInt
4
>>> b.myList[2] = 3
>>> b.myInt = 3
>>> b.myList
[4, 4, 3, 4]
>>> b.myInt
3
>>> a.myList
[4, 4, 3, 4]
>>> a.myInt
4
I would not expect the second a.myList to have changed as it did
since, for me, I have only changed b.myList. And also, why only the
list changed and not the integer?
One thing i tried was:
>>> class Test2:
myList = []
myInt = 4
def __init__(self):
self.myList = [4 for n in range(4)]
>>> a = Test2()
>>> b = Test2()
>>> a.myList
[4, 4, 4, 4]
>>> b.myList
[4, 4, 4, 4]
>>> b.myList[2] = 3
>>> b.myList
[4, 4, 3, 4]
>>> a.myList
[4, 4, 4, 4]
And as you see it worked as I expected.
Now the question, why?
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