Python counting string

Maybe you want this:

def letterCount(text,collection):
    res = 0
    for c in text:
        if c in collection:
            res = res + 1
    return res
seuss = 'The cat in a hat came back'
letters = 'ac'
print(letterCount(seuss,letters))

you define an variable collection in for collection in text:, it hidden the variable in def letterCount(text,collection).

I think the syntax of the python code you wrote is wrong. this is most probably what you want

def letterCount(text,collection):
  for collection in text:
    if collection in text:
        return len(collection) + 1
seuss = 'The cat in a hat came back'
Letters = 'ac'
print(letterCount(seuss,Letters))

your question is also not clear. can you elaborate a little. if what you want is to count the number of words in the string this would suffice

print len(seuss.split(' '))

If you want to count the number of times the string letters occurs in seuss:

def letterCount(text,collection):
    count = 0

    for i in range(0, len(text) - len(collection)):
        if collection == text[i:i + len(collection)]:
            count += 1

    return count

seuss = 'The cat in a hat came back'
letters = 'ac'
print(letterCount(seuss,letters))

If you want to count the number of times each letter in letters occurs in seuss:

def letterCount(text,collection):
    count = 0

    for i in range(0, len(text)):
        for c in collection:       
            if c == text[i]:
                count += 1

    return count

seuss = 'The cat in a hat came back'
letters = 'ac'
print(letterCount(seuss,letters))

Assuming you want to count the number of letters in the sentence, I'd do this:

def letterCount(text,collection):
  lettercount = 0
  for letter in collection:
    lettercount += text.count(letter)
  return lettercount


seuss = 'The cat in a hat came back'
Letters = 'ac'
print(letterCount(seuss,Letters)) # Returns 8

Explanation:

lettercount = 0 sets our counter to 0

for letter in collection: creates a loop through the list of the letters you passed to the function. In this case "a" and "c"

lettercount += text.count(letter) counts the number of times each letter appears in the sentence and adds it to the counter.

return lettercount sends the result back.

If you want to find out the number of times either 'a' or 'c' comes in 'The cat in a hat came back', then:

import collections
def letter_count(text, letters):
    counter = collections.Counter(text)
    return sum(counter.get(letter, 0) for letter in letters)

Try this:

import re
def letterCount(text,collection):
    return sum(len(re.findall(c, text)) for c in collection)

# re.findall(c, text) -> find all occurences of letter c in text
# len(...)            -> get the length of the list of all occurrences of c in text
# sum(...)            -> sum up all the partial results