# KeyError when finding for max value in nested dictionary

I have a nested dictionary like this:

```
input_dic = {'GCT': {'A': '2.520'},
'GCC': {'A': '1.294'},
'GCA': {'A': '0.161'},
'GCG': {'A': '0.025'},
'TGT': {'C': '1.422'},
'TGC': {'C': '0.578'},
'GAT': {'D': '0.645'}}
```

I want to extract per group max value, like `'A'`

is `2.520`

, so I tried:

```
max(float(x['A']) for x in input_dic.values())
```

However, it said `KeyError: 'A'`

. I think that this occurs because this key is not unique, but I have no idea how to fix it.

I tried a new method to build the dictionary like

```
{('A', 'GCT'): '2.520',
('A', 'GCC'): '1.294',
('A', 'GCA'): '0.161',
('A', 'GCG'): '0.025',
('C', 'TGT'): '1.422',
('C', 'TGC'): '0.578',
('D', 'GAT'): '0.645'}
```

but I also have no idea to extract group `'A'`

is `2.520`

. Please tell me if you know how to do it.

## Have an answer?

JD