i am puzzled by this behavior
r,c = (5,2)
slist = [[0]*c]*r
print(slist)
for i in range(r):
slist[i][0] = i
print(slist)
Output is
[[0, 0], [0, 0], [0, 0], [0, 0], [0, 0]]
[[4, 0], [4, 0], [4, 0], [4, 0], [4, 0]]
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1How are you puzzled by this behaviour?Ayush Garg– Ayush Garg2020-11-29 17:06:32 +00:00Commented Nov 29, 2020 at 17:06
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May be I am losing my mind. I wanted to assign (0,0)-th element to 0, (1,0)-th element to 1, (2,0)-th element to 2, ...gsakthivel– gsakthivel2020-11-29 17:08:43 +00:00Commented Nov 29, 2020 at 17:08
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1 Answer
When you do [[0] * c] * r, you create a list where every element is a reference to the same list. So, when you change one, they all change. Use a list comprehension with a range instead to create unique lists:
slist = [[0] * c for _ in range(r)]
See here for more info.
