How can I remove function's 'none' output?

Question

import random
def random_value(x,y):
    y = ord(y)+x
    return chr(y)
def random_value1(x,y):
    y = ord(y)-x
    return chr(y)
def encryption(a,b):
    infile = open("e:\\temp\\security.txt","r")
    outfile = open("e:\\temp\\"+a+".txt","w")
    security = infile.read()
    for i in security:
        outfile.write(random_value(b,i))
    print("encryption success")
    infile.close()
    outfile.close()
def decryption(a,b):
    c = input("decryption file name : ")
    infile = open("e:\\temp\\"+c+".txt","r")
    outfile = open("e:\\temp\\"+a+".txt","w")
    security = infile.read()
    for i in security:
        outfile.write(random_value1(b,i))
    print("decryption success")    
    infile.close()
    outfile.close()
while True:
    a=input("encryption / decryption  : ")
    if not a:
        break
    b=input("file name : ")
    c=int(input("secret key : "))
    if a=="encryption":
        print(encryption(b,c))
    elif a=="decryption":
        print(decryption(b,c))
    else:
        break

Answer 1

In line 36 and 38,
write encryption(b, c) instead of print(encryption(b, c))

write decryption(b, c) instead of print(decryption(b, c))