Jul-09-2020, 12:50 PM
Depending on how I initialize an array its behaviour is different and in one case seems like a Python bug. In my example I create two 3 X 10 arrays using different techniques. I then set elements of these arrays to a value and print them out with surprising results. Here is my code:
x=[[0]*4]*10 y=[ [ 0 for i in range( 4 ) ] for j in range( 10 ) ] if x==y: print("same") for i in range(10): x[i][0]=i y[i][0]=i print(x) print(y)After running this code x and y should be the same but they are not. What am I doing wrong? Obviously, I will not use:
x=[[0]*4]*10in the future. Nevertheless it is perplexing.
Output:Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:20:19) [MSC v.1925 32 bit (Intel)] on win32
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>>>
= RESTART: C:\Users\John PC 2017\AppData\Local\Programs\Python\Python37\test.py
same
[[9, 0, 0, 0], [9, 0, 0, 0], [9, 0, 0, 0], [9, 0, 0, 0], [9, 0, 0, 0], [9, 0, 0, 0], [9, 0, 0, 0], [9, 0, 0, 0], [9, 0, 0, 0], [9, 0, 0, 0]]
[[0, 0, 0, 0], [1, 0, 0, 0], [2, 0, 0, 0], [3, 0, 0, 0], [4, 0, 0, 0], [5, 0, 0, 0], [6, 0, 0, 0], [7, 0, 0, 0], [8, 0, 0, 0], [9, 0, 0, 0]]
>>>