compiling pattern inside another pattern using python regex

Question

I would like to compile python regex inside another regex. for example find IP address like this below: This does not seem to work.

 >>> import re 
    >>> p_ip = re.compile(r'[0-9]|[0-9][0-9]|1[0-9][0-9]|2[0-5][0-5]')
    >>> p_ip_full =re.compile( r'^(p_ip)\.{3}p_ip$')
    >>> ip_str = "255.123.123.12"
    >>> if (p_ip_full.match(ip_str)):
    ...     print("match")
    ...
    >>> p_ip_full
    re.compile('^(p_ip)\\.{3}p_ip$')

SCB · Accepted Answer · 2018-01-03 00:38:55Z

2

In your case p_ip is simply looking for the literal characters p_ip. Use .format() to add the value in. You don't even need to wrap the first part in a re.compile, treat it as a normal string.

p_ip = r'[0-9]|[0-9][0-9]|1[0-9][0-9]|2[0-5][0-5]'
p_ip_full = re.compile(r'^({0})\.{{3}}{0}$'.format(p_ip))

Note that you need to encase {3} in a double {{ }} so it gets escaped.

answered Jan 3, 2018 at 0:38

SCB

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