# strange result when finding the index of a boolean list

John Palmieri suggest to use v.startswith('$a_') in answer to my former question `How to construct a condition on the family name of a variable without notice to its index`

.

Here is a little program

```
RR=['$x_{0}$',
'$x_{1}$',
'$x_{2}$',
'$a_{3}$',
'$\\varepsilon_{4}$',
'$a_{5}$',
'$\\varepsilon_{6}$']
OB=[v.startswith('$a_') for v in RR]
SS=[OB.index(v) for v in OB if v==True]
SS
```

which give the answer `[3,3]`

when in my eyes the answer should be `[3,5]`

. I know this is the standard process to gives the first occurence of the string. But why there is not a defined function which gives all the indexes ?