astring = 'thisisashorttext'
astring.count('t')
# Out: 4
This works even for substrings longer than one character:
astring.count('th')
# Out: 1
astring.count('is')
# Out: 2
astring.count('text')
# Out: 1
which would not be possible with collections.Counter
which only counts single characters:
from collections import Counter
Counter(astring)
# Out: Counter({'a': 1, 'e': 1, 'h': 2, 'i': 2, 'o': 1, 'r': 1, 's': 3, 't': 4, 'x': 1})