I have the following piece of code
>>> no=[]
>>> matrix = [[[] for x in xrange(4)] for x in xrange(4)]
>>> no=[2]
>>> temp = no
>>> matrix[1][2].append(temp)
>>> no.append(3)
>>> matrix[1][2]
when I print matrix[1][2] I am getting the following output:
[[2, 3]]
But what I want is:
[2]
So basically what is happening is the list is getting changed inside the matrix list if I change it afterwards. But I don't want to get it changed
How can I do it ? And why is it happening ?
Make a copy of no temp = no[:].
temp = no is just a reference to the same object so any changes in no will affect temp
A reference:
In [21]: my_l = [1,2,3]
In [22]: ref_my_l = my_l
In [23]: ref_my_l
Out[23]: [1, 2, 3]
In [24]: my_l.append(4)
In [25]: my_l
Out[25]: [1, 2, 3, 4]
In [26]: ref_my_l
Out[26]: [1, 2, 3, 4]
A copy:
In [27]: my_l = [1,2,3]
In [28]: copy_my_l = my_l[:]
In [29]: my_l.append(4)
In [30]: my_l
Out[30]: [1, 2, 3, 4]
In [31]: copy_my_l
Out[31]: [1, 2, 3]