python - how to find letters that don't occur in either string? -

i need write code prints out letters don't appear in either of 2 strings. have opposite. prints out letters occur in both strings. here code. i'm not sure how change it.

s1 = input('enter string:\n') s2 = input('enter second string:\n') s1 = set(s1) s2 = set(s2)  def notinother(s1, s2):     chars = []     char in (s1,s2):         if char not in s2:             if char not in s1:                 chars.append(char)     print(chars) 

here i'm trying write simple , basic answer.

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a string containing ascii letters can found in string module

from string import ascii_letters letters 

but of course can write directly in code

letters = 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz' 

you need 2 strings characters excluded

s1, s2 = 'abcdef', 'stuvwxyz' 

to solve problem, can build list remaining letters using list comprehension (i think code self explanatory)

rl = [c c in letters if c not in s1+s2] 

eventually, if want print result of code can use .join() method of null string

print(''.join(rl)) 

that gives you

ghijklmnopqrstuvwxyzabcdefghijklmnopqr