Alternative

from collections import defaultdict

def letter_frequency(s):

frequency_dict = defaultdict(lambda : 0)

for char in s.lower():

if char.isalpha():

frequency_dict[char] += 1

f = [ (ch, round(freq/len(s),4)) for ch, freq in frequency_dict.items()]

f.sort(key = lambda x: (-x[1], x[0]))

return f

freq = letter_frequency(open("1984.txt").read())

print(freq)