counting the letters

# Write a code snippet that inputs a sentence from the user, then uses a dictionary to 
# summarize the number of occurrences of each letter. Ignore case, ignore blanks and assume 
# the user doesnot enter any punctuation. Display a two-column table of the letters and their
# counts with the letters in sorted order.
# Example:
# Input >>> "This is a sample text with several words This is more sample text with some differentwords" 
# Output >>> [('a', 4), ('d', 3), ('e', 10), ('f', 2), ('h', 4), ('i', 7), ('l', 3), ('m', 4), 
#             ('n', 1), ('o', 4), ('p', 2), ('r', 5), ('s', 10), ('t', 9), ('v', 1), ('w', 4), ('x', 2)] 

# string modulu yuklenerek kucuk harfler alinmistir.
import string

cumle=str(input("bir cumle giriniz: "))
kucuk_harfler=list(string.ascii_lowercase)
cumle=cumle.lower() # girilen string kucuk harflere donusturulmustur.
son={}

#ilk for loopu ile listedeki tum elemanlar bir defa kontrol edilerek sozluge eklenmistir.
for i in range(len(cumle)):
    if cumle[i] in kucuk_harfler:
        son[cumle[i]]=0
        
#ikinci for loopu ile bir onceki for loopu ile sozluge eklenen elemanlardan kac tane bulundugu tespit edilmektedir.        
for i in range(len(cumle)):
    if (cumle[i] in kucuk_harfler) and cumle[i]!=0:
        son[cumle[i]] += 1
print(son)