# credit to Stack Overflow user in the source link
# finds isolated alphabetical characters
import re
s = "fish oil B stack peanut c "

words = re.finditer('\S+', s)
has_alpha = re.compile(r'[a-zA-Z]').search
for word in words:
    if len(word.group()) == 1 and has_alpha(word.group()):
        print(word.start()) # prints the index inside the string