Why are these two values different when I assign one to the other?

The code below gives different values for c and d when I print them

import csv

datafile = open('test1.csv', 'r')开发者_StackOverflow中文版
datareader = csv.reader(datafile)
c = []
for row in datareader:
    c.append(row)

d = [[0]*2]*2
i=0

while i < 2:

    j=0

    while j < 2:

        d[i][j] = float(c[i][j])

        j=j+1
    i=i+1

print(c)
print(d)

This line:

d = [[0]*2]*2

doesn't create copies of the inner lists, it just creates multiple references to the same list. Replace it with an explicit declaration:

d = [[0, 0], [0, 0]]

Lists are mutable elements. You're not creating multiple lists when you do things like [[0]]*10 but creates 10 references to the same object.