caesar encryption

def caesar_encryption(st, shift, num):
    new = st.lower()
    result = ""
    if shift=='l':
        for i in new:
            if i.isalpha():
                if ord(i)-num<97:
                    result = result + chr(122-(97-(ord(i)-num) +1))
                else:
                    result = result + chr(ord(i)-num)
            else:
                result = result + i
    
    elif shift=='r':
        for i in new:
            if i.isalpha():
                if ord(i)+num>122:
                    result = result + chr(97 + ((ord(i)+num)-122 -1))
                else:
                    result = result + chr(ord(i)+num)
            else:
                result = result + i
    
    return result

st = input("Enter the message to be encrypted: ")
shift = input("Enter 'l' or 'r' to mention direction of shift: " )
num = int(input("Enter number of shifts: "))

print("The encrypted message is : ",caesar_encryption(st, shift, num))