Number and letter replacement are mixed up with custom substitution cipher in Python

This part of the code transfers the letters to numbers and then multiply it by the key (datetime*ip (replaced(.,5)

import datetime
import time 
import socket
while (True):
IP=int(socket.gethostbyname(socket.gethostname()).replace(".","5"))
time=(int(datetime.datetime.now().strftime("%Y%m%d%H%M%S")))
qw=(int(str((time)+(IP))))
a=int("934")*1
b=int("346")*1
c=int("926")*1
d=int("9522")*1
e=int("7334")*1
f=int("5853")*1
g=int("2432")*1
h=int("2027")*1
i=int("7024")*1
j=int("828")*1
k=int("798")*1
m=int("593")*1
n=int("662")*1
l=int("5950")*1
o=int("357")*1
p=int("506")*1
q=int("239")*1
r=int("99")*1
s=int("372")*1
t=int("636")*1
u=int("553")*1
v=int("255")*1
w=int("298")*1
x=int("8822")*1
y=int("458")*1
z=int("659")*1
space=("633")
msg=input("")
msg=msg.replace("a",(str(a)))
msg=msg.replace("b",(str(b)))
msg=msg.replace("c",(str(c)))
msg=msg.replace("d",(str(d)))
msg=msg.replace("e",(str(e)))
msg=msg.replace("f",(str(f)))
msg=msg.replace("g",(str(g)))
msg=msg.replace("h",(str(h)))
msg=msg.replace("i",(str(i)))
msg=msg.replace("j",(str(j)))
msg=msg.replace("k",(str(k)))
msg=msg.replace("m",(str(m)))
msg=msg.replace("n",(str(n)))
msg=msg.replace("l",(str(l)))
msg=msg.replace("o",(str(o)))
msg=msg.replace("p",(str(p)))
msg=msg.replace("q",(str(q)))
msg=msg.replace("r",(str(r)))
msg=msg.replace("s",(str(s)))
msg=msg.replace("t",(str(t)))
msg=msg.replace("u",(str(u)))
msg=msg.replace("v",(str(v)))
msg=msg.replace("w",(str(w)))
msg=msg.replace("x",(str(x)))
msg=msg.replace("y",(str(y)))
msg=msg.replace("z",(str(z)))
msg=msg.replace(" ",(str(space)))
msg=int(msg)
msg=int(msg)*(qw)
fileb=open("key.txt","w")
filec=fileb.write(str(qw))
fileb.close()
file=open("msg decrypt.txt","w")
filea=file.write(str(msg))
file.close()
print (msg)

decryption code this is where the problem is when replacing the number back to letters

file=open("msg decrypt.txt","r")
encrypted_msg=int(file.read())
print(encrypted_msg)
file.close()
fileb=open("key.txt","r")
key=int(fileb.read())
fileb.close()
encrypted_msg=(int(encrypted_msg)-(key))
encrypted_msg=(int(encrypted_msg)/(key))
encrypted_msg=(int(encrypted_msg)+1)
print(encrypted_msg)
a=("934")
b=("346")
c=("926")
d=("9522")
e=("7334")
f=("5853")
g=("2432")
h=("2027")
i=("7024")
j=("828")
k=("798")
m=("593")
n=("662")
l=("5950")
o=("357")
p=("506")
q=("239")
r=("99")
s=("372")
t=("63")
u=("55")
v=("255")
w=("298")
x=("8822")
y=("458")
z=("659")
space=("633")
ab=str(encrypted_msg)
if (a) in ab:
    ab=ab.replace(str(a),"a")
if ("346") in ab:    
    ab=ab.replace(str(b),"b")    
if ("926") in ab:    
    ab=ab.replace(str(c),"c")
if ("9522") in ab:
    ab=ab.replace(str(d),"d")
if ("7334") in ab:
    ab=ab.replace(str(e),"e")
if ("5853") in ab:
    ab=ab.replace(str(f),"f")
if ("2432") in ab:    
    ab=ab.replace(str(g),"g")
if ("2027") in ab:
    ab=ab.replace(str(h),"h")
if ("7024") in ab:
    ab=ab.replace(str(i),"i")
if ("828") in ab:
    ab=ab.replace(str(j),"j")
if ("798") in ab:
    ab=ab.replace(str(k),"k")
if ("593") in ab:
    ab=ab.replace(str(m),"m")
if ("662") in ab:
    ab=ab.replace(str(n),"n")
if ("5950") in ab:
    ab=ab.replace(str(l),"l")
if ("357") in ab:
    ab=ab.replace(str(o),"o")
if ("506") in ab:
    ab=ab.replace(str(p),"p")
if ("239") in ab:
    ab=ab.replace(str(q),"q")
if ("99") in ab:
    ab=ab.replace(str(r),"r")
if ("372") in ab:
    ab=ab.replace(str(s),"s")
if ("636") in ab:
    ab=ab.replace(str(t),"t")
if ("553") in ab:    
    ab=ab.replace(str(u),"u")
if ("255") in ab:
    ab=ab.replace(str(v),"v")
if ("298") in ab:
    ab=ab.replace(str(w),"w")
if ("8822") in ab:
    ab=ab.replace(str(x),"x")
if ("458")in ab:
    ab=ab.replace(str(y),"y")
if ("659") in ab:
    ab=ab.replace(str(z),"z")
if ("633") in ab:
    ab=ab.replace(str(space)," ")          
print(ab)

The program encrypts just fine. However, it only decrypts 4 letters anything more it comes out as jumbled letters and numbers.