Add 0 to hostname

Question

My file contains IP addresses that I'd like to convert to host names. The IP addresses are the same except for the last three octets. For example:

192.168.38.8
192.168.38.9
192.168.38.10

I have the following code in my python script to substitute the IP address with the host name which ends in the final octet.

 hostname = re.sub('192.168.38.','Host-Name',lm.group(4))

This give me the results:

Host-Name8
Host-Name9
Host-Name10

How do I get the single digit octets to have a leading zero? The desired output would be;

Host-Name08
Host-Name09
Host-Name10

Possible duplicate of [Best way to format integer as string with leading zeros?](https://stackoverflow.com/questions/733454/best-way-to-format-integer-as-string-with-leading-zeros) — Barmar, Sep 07 '17 at 16:11
ideally, it should consider **3** digits, according to octet size. `Host-Name008` ... — RomanPerekhrest, Sep 07 '17 at 16:12
Possible duplicate of [Display number with leading zeros](https://stackoverflow.com/questions/134934/display-number-with-leading-zeros) — CDspace, Sep 07 '17 at 16:14

score 0 · Accepted Answer · edited Sep 07 '17 at 16:48

0

re.sub isn't used correctly.

From documentation for re.sub, you can pass a string or replacement function that returns a string when a match is found.

Notice: You can use any of the methods in answers to questions in the duplicate flags to pad single digits.

def replace_ip(match):
    last_octet = match.group(1)

    return "".join((
        'Host-Name',
        last_octet.zfill(2)
    ))


re.sub(r'192.168.38.(\d+)', replace_ip, ips_from_file)

edited Sep 07 '17 at 16:48

John Kugelman

349,597
67
533
578

answered Sep 07 '17 at 16:26

Oluwafemi Sule

36,144
1
56
81

@ Oluwafemi Sule - Worked perfectly. Thank you. – teamg Sep 07 '17 at 18:06

score 0 · Answer 2 · answered Sep 07 '17 at 17:47

0

You might find just using split() easier as follows:

for ip_addr in ["192.168.38.8", "192.168.38.9", "192.168.38.10"]:
    print "Host-Name{:02}".format(int(ip_addr.split('.')[3]))

This would give you:

Host-Name08
Host-Name09
Host-Name10

answered Sep 07 '17 at 17:47

Martin Evans

45,791
17
81
97

Add 0 to hostname

2 Answers2