Как реализовать шифрование и дешифрование ceaser cipher в одной функции?

Hi Below are my codes for encryption and decryption.

import ast
a = ast.literal_eval(input())
n1 = a[0]
n2 = a[1]
def encryption(string,step):
    result = ''
    for i in string:
        if i == "":
            result = result+i
        elif i.isupper():
            result = result + chr((ord(i) + step - 65) % 26 + 65)
        else:
            result = result + chr((ord(i) + step - 97) % 26 + 97)
    return result
print(encryption(n1,n2))

Input: n1 = upHrae, n2 = 4
Output: ytLvei




#Program for Decryption

def decryption(string1,step):
    result1 = ''
    for j in string1:
        if j == "":
            result1 = result1+i
        elif j.isupper():
            result1 = result1 + chr((ord(i) + step + 65) % 26 + 65)
        else:
            result1 = result1 + chr((ord(i) + step + 97) % 26 + 97)

    return result1
print(drcryption(n1,n2))

input: n1 = banana, n2 = 7
output: utgtgt


I want to combine both encryption and decryption function in one function which generates output as 'ytLvei' when input is 'n1 = upHrae, n2 = 4' and generates output as 'utgtgt' when input is 'n1 = banana, n2 = 7.'



Please help me.

I tried Below code but it is not working as expected.



import ast
n = ast.literal_eval(input())
n1 = n[0]
step = n[1]
def enc_dec(string,step):
    result = ''
    for i in string:
        if ((ord(i) + step)>=65) or ((ord(i) + step)<=97):
            if i=='':
                result = result+i
            elif i.isupper():
                result = result + chr((ord(i) + step - 65) % 26 + 65)
            else:
                result = result + chr((ord(i) + step - 97) % 26 + 97)

        if ((ord(i) + step)>=97) or ((ord(i) + step)<=122):
            if i=='':
                result = result+i
            elif i.isupper():
                result = result + chr((ord(i) + step + 65) % 26 + 65)
            else:
                result = result + chr((ord(i) + step + 97) % 26 + 97)    
    return result

print(enc_dec(n1,step))