### Question :

I’ve been tinkering in python this week and I got stuck on something.

If I had a 2D list like this:

```
myList = [[1,2],[3,4],[5,6]]
```

and I did this

```
>>>myList.index([3,4])
```

it would return

```
1
```

However, I want the index of something in side one of the lists, like this

```
>>>myList.index(3)
```

and it would return

```
1, 0
```

Is there anything that can do this?

Cheers

##
Answer #1:

Try this:

```
def index_2d(myList, v):
for i, x in enumerate(myList):
if v in x:
return (i, x.index(v))
```

Usage:

```
>>> index_2d(myList, 3)
(1, 0)
```

##
Answer #2:

If you are doing many lookups you could create a mapping.

```
>>> myList = [[1,2],[3,4],[5,6]]
>>> d = dict( (j,(x, y)) for x, i in enumerate(myList) for y, j in enumerate(i) )
>>> d
{1: (0, 0), 2: (0, 1), 3: (1, 0), 4: (1, 1), 5: (2, 0), 6: (2, 1)}
>>> d[3]
(1, 0)
```

##
Answer #3:

There is nothing that does this already, unless it’s in numpy, which I don’t know much about. This means you’ll have to write code that does it. And that means questions like “What does `[[1, 2], [2, 3], [3, 4]].index(3)`

return?” are important.

##
Answer #4:

Using simple genexpr:

```
def index2d(list2d, value):
return next((i, j) for i, lst in enumerate(list2d)
for j, x in enumerate(lst) if x == value)
```

### Example

```
print index2d([[1,2],[3,4],[5,6]], 3)
# -> (1, 0)
```

##
Answer #5:

```
def td(l,tgt):
rtr=[]
for sub in l:
if tgt in sub:
rtr.append( (l.index(sub),sub.index(tgt)) )
return rtr
myList = [[1,2],[3,4],[5,6]]
print td(myList,3)
```

This will return more than one instance of the sub list, if any.

##
Answer #6:

*Try this! this worked for me đź™‚*

```
def ret_pos(mylist,val_to_find):
for i in (len(mylist)):
for j in (len(i)):
if mylist[i][j]== val_to_find:
postn=[i,j]
return(postn);
```

##
Answer #7:

Based on kevpie’s answer I managed to get a 2D list containing the coordinates of all occurences

```
myList = [[0,1],[1,1],[0,0],[1,0]]
coordsList = [[x, y] for x, li in enumerate(myList) for y, val in enumerate(li) if val==1]
```

Now coordsList contains all indexes for value 1 in myList :

```
[[0, 1], [1, 0], [1, 1], [3, 0]]
```