validate ip address python

1Validate IP Address Python:
2
3def ip_checkv4(ip):
4        parts=ip.split(".")
5        if len(parts)<4 or len(parts)>4:
6            return "invalid IP length should be 4 not greater or less than 4"
7        else:
8            while len(parts)== 4:
9                a=int(parts[0])
10                b=int(parts[1])
11                c=int(parts[2])
12                d=int(parts[3])
13                if a<= 0 or a == 127 :
14                    return "invalid IP address"
15                elif d == 0:
16                    return "host id  should not be 0 or less than zero " 
17                elif a>=255:
18                    return "should not be 255 or greater than 255 or less than 0 A"
19                elif b>=255 or b<0: 
20                    return "should not be 255 or greater than 255 or less than 0 B"
21                elif c>=255 or c<0:
22                    return "should not be 255 or greater than 255 or less than 0 C"
23                elif d>=255 or c<0:
24                    return "should not be 255 or greater than 255 or less than 0 D"
25                else:
26                    return "Valid IP address ", ip
27        
28    p=raw_input("Enter IP address")
29    print ip_checkv4(p)