import operator
def sort_table(table, col):
return sorted(table, key=operator.itemgetter(col))
x = [
[4, 6, 3],
[7, 5, 2],
[1, 3, 8]
]
y = sort_table(x[0:3], 0)
for i in range(3):
for j in range(3):
print x[i][j],'\t',
print('\n')
for i in range(3):
for j in range(3):
print y[i][j],'\t',
print('\n')
x[0][0]=y[0][0]
x[1][0]=y[1][0]
x[2][0]=y[2][0]
print x
Result value is
[[1, 6, 3], [1, 5, 2], [1, 3, 8]]
It comes out as
[[1,6,3],[4,5,2],[7,3,8]]
Shouldn't it come out as?
python
Typical show copy problem. Although x and y appear to be unrelated, in fact, x and y are reference relationships. So if you change x, y can be affected, and vice versa.
def sort_table(table, col):
return sorted(table, key=operator.itemgetter(col))
x = [ [4, 6, 3], [7, 5, 2], [1, 3, 8] ]
y = sort_table(x[0:3], 0)
print "original:"
print y
print "after x[0][0]=y[0][0]:"
x[0][0]=y[0][0]
print y
Execution result:
original:
[[1, 3, 8], [4, 6, 3], [7, 5, 2]]
after x[0][0]=y[0][0]:
[[1, 3, 8], [1, 6, 3], [7, 5, 2]]
If you run this code, you'll get the hang of it. You only changed the value for x, but y[1][0] is also changed. If [[1,6,3],[4,5,2],[7,3,8]] appears when you run the uploaded code, replace the function sort_table as follows.
from copy import deepcopy
def sort_table(table, col):
return deepcopy(sorted(table, key=operator.itemgetter(col)))
The deepcopy function used here breaks the rings of x and y to prevent further reference from occurring. How do I copy How do I copy the Python list? You can check it out at .
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