In [33]: x=[[]]*6
In [34]: x
Out[34]: [[], [], [], [], [], []]
In [35]: x[0]
Out[35]: []
In [36]: x[0].append(1)
In [37]: x
Out[37]: [[1], [1], [1], [1], [1], [1]]
I just append 1 to x[0], but why do all lists in the list x change?
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Arpit Solanki
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user9412567
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I think pass by reference is something you should read about – Arpit Solanki Feb 26 '18 at 10:05
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`x=[[]]*6` creates a list with *6 references to the same empty list*. – juanpa.arrivillaga Feb 26 '18 at 10:06
1 Answers
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This happens because x is a list of references to the same inner list.
To create a list of 6 different empty lists, you can use list comprehension:
a = [[] for _ in range(6)]
Phydeaux
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@user9412567 no problem. see update for how to achieve what you wanted – Phydeaux Feb 26 '18 at 10:14