Python - How to change values in a list of lists?

Question

I have a list of lists, each list within the list contains 5 items, how do I change the values of the items in the list? I have tried the following:

    for [ite         


        

Answer 1

Changing the variables assigned in the for does not change the list. Here's a fairly readable way to do what you want:

execlist = [
    #itemnumber, ctype, x, y, delay
    [1, 2, 3, 4, 5],
    [6, 7, 8, 9, 10],
    [11, 12, 13, 14, 15],
]

mynumber, myctype, myx, myy, mydelay = 6, 100, 101, 102, 104

for i, sublist in enumerate(execlist):
   if sublist[0] == mynumber:
        execlist[i] = [mynumber, myctype, myx, myy, mydelay]

print execlist

Output:

[[1, 2, 3, 4, 5], [6, 100, 101, 102, 104], [11, 12, 13, 14, 15]]

Answer 2

The iterator variables are copies of the original (Python does not have a concept of a reference as such, although structures such as lists are referred to by reference). You need to do something like:

for item in execlist:
    if item[0] == mynumber:
        item[1] = ctype
        item[2] = myx
        item[3] = myy
        item[4] = mydelay

item itself is a copy too, but it is a copy of a reference to the original nested list, so when you refer to its elements the original list is updated.

This isn't as convenient since you don't have the names; perhaps a dictionary or class would be a more convenient structure.