Is it possible to replace `1` with `2` using a regex? The values in the first brackets will always be whole numbers. I started doing this using `str.split('[')` and realised that's not the best way.

EDIT - the value in the first brackets can be any whole number. This string is basically the name attribute of a form field in a big dynamic form. The form is made up of fields in rows and the number in the first brackets indicated the row. A new line of fields is added by cloning the last row but the row index needs to be updated in the name attribute. 

```
value[1][some_string]

```