python - Determing relative letter frequency -

i need create function takes text file input , returns vector of size 26 frequency in percent of each character (a z). must insensitive case. other letters (ex. å) , symbols should ignored.

i've tried use of answers here, answer 'jacob'. determining letter frequency of cipher text

this code far:

def letterfrequency(filename):     #f: text file converted lowercase      f=filename.lower()     #n: sum of letters in text file     n=float(len(f))     import collections     dic=collections.defaultdict(int)     #the absolute frequencies     x in f:         dic[x]+=1     #the relative frequencies     string import ascii_lowercase     x in ascii_lowercase:         return x,(dic[x]/n)*100 

for example, if try this:

print(letterfrequency('i have no idea')) >>> ('a',14.285714) 

why not print relative values of letters? letters not in string, z in example?

and how make code print vector of size 26?

edit: have tried using counter, prints ('a':14.2857) , letters in mixed order. need relative frequency of letters in ordered sequence!

for x in ascii_lowercase:     return x,(dic[x]/n)*100 

the function returned in first iteration of loop.

instead, change return list of tuples:

letters = [] x in ascii_lowercase:     letters.append((x,(dic[x]/n)*100)) return letters