Python – Counting Letter Frequency in a String

I want to write my each string’s letter frequencies. My inputs and expected outputs are like this.

"aaaa" -> "a4"
"abb" -> "a1b2"
"abbb cc a" -> "a1b3 c2 a1"
"bbbaaacddddee" -> "b3a3c1d4e2"
"a   b" -> "a1 b1"

I found this solution but it gives the frequencies in random order. How can I do this?

>Solution :

Does this satisfy your needs?

from itertools import groupby
s = "bbbaaac ddddee aa"

groups = groupby(s)
result = [(label, sum(1 for _ in group)) for label, group in groups]
res1 = "".join("{}{}".format(label, count) for label, count in result)
# 'b3a3c1 1d4e2 1a2'

# spaces just as spaces, do not include their count
import re
re.sub(' [0-9]+', ' ', res1)
'b3a3c1 d4e2 a2'