Character occurrence count

# Count occurrence of character in a string.
# Ex: 'Hello World!' would have 2 'o'

import itertools
S = 'Hello World!'

# Sort the string so each character comes consecutively
srt = ''.join(sorted(S))

# Group each characters
grp = [ ''.join(grp) for num, grp in itertools.groupby(srt)]

# Count each group
hasil = map(lambda x: (x[0], len(x)), grp)