Python Challenge #2 - Solution

While there can be n no. of possible ways to solve the python challenge #2, following is the solution I could come up with.
 
chars =list("abcdefghijklmnopqrstuvwxyz")
inp = list("g fmnc wms bgblr rpylqjyrc gr zw fylb. rfyrq ufyr amknsrcpq ypc dmp. bmgle gr gl zw fylb gq glcddgagclr ylb rfyr'q ufw rfgq rcvr gq qm jmle. sqgle qrpgle.kyicrpylq() gq pcamkkclbcb. lmu ynnjw ml rfc spj.")
 
for ori in inp:
    for tobe in chars:
        if ori== " " or ori== ".":
            print(ori,end ="")
        elif ori == tobe:
                if tobe == "z":
                    print("b",end="")
                elif tobe =="y":
                    print("a",end="")
                else:
                    a =chars.index(tobe)
                    b = a+2
                    print(chars[b],end="")