I have a DNA sequence:

```
seq='AACGTTCAA'

```

I want to count how many letters are equal to the next one. In this example I should get 3 (because of AA-TT-AA).

In my first try I found out that this doesn't work, because i is a string and 1 an integer.

```
seq='AACGTTCAA'
count=[]
for i in seq:
    if i == i+1: #neither i+=1
        count.append(True)
    else: count.append(False)
print(sum(count))  

```

So I tried this:

```
seq='AACGTTCAA'
count=[]
for i in seq:
    if i == seq[seq.index(i)+1]:
        count.append(True)
    else: count.append(False)
print(sum(count))  

```

Then I receive this output which I cannot understand.
3 of these True should be False (1,5,8) Especially 8 as it is the last element of the string.

```
6
[True, True, False, False, True, True, False, True, True] 

```

If thought about doing this with arrays but I think there might be a easy way to do this just in strings. Thanks