As a beginner using Python, I'm trying to populate a dictionary with values using an if statement. If you have ideas as to why this isn't working, I would appreciate your input. Mahalo in advance!

```
#first list
groslist = [0, 1, 2, 3]
#dictionary whose keys are items in grosList
grosdict = {k:[] for k in groslist}
#second list whose items correspond with dictionary's keys
indivlist = [0, 0, 1, 0, 1, 1, 1, 2, 2, 2, 2, 3, 3]
#third list whose nth item ID corresponds indivlist
indivIDlist = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

#Populate dictionary with indivIDlist values (dict keys correspond with indivlist items)
for ID in indivlist:
    for ID in groslist:
        x = 0;
        if indivlist[x] == groslist[x]:
            grosdict[indivlist[x]] = indivIDlist[x];
        x += 1

```

Here is my ideal output:

```
print CG_IDdict
{0: [0, 1, 3], 1: [2, 4, 5, 6], 2: [7, 8, 9, 10], 3: [11, 12]}

```