Rewriting elements in a loop of lists (Python)

Hello. In Python, in a loop of lists, a = [-1] `` `does not rewrite the original list, but a [0] = -1``` Rewrite.

alist = [[0], [0], [0]]
for a in alist:
  a = [-1]

print(alist)  # ==>  [[0], [0], [0]]

for a in alist:
  a[0] = -1

print(alist)  # ==>  [[-1], [-1], [-1]]

$ python3 -V
Python 3.7.7

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