Using re.VERBOSE, and re-using components of regex?

[MRAB]

On 17/04/2013 00:45, Victor Hooi wrote:
> Hi,
>
> I'm trying to compile a regex Python with the re.VERBOSE flag (so that I can add some friendly comments).
>
> However, the issue is, I normally use constants to define re-usable bits of the regex - however, these doesn't get interpreted inside the triple quotes.
>
> For example:
>
>      import re
>
>      TIMESTAMP = r'(?P<timestamp>\d{2}:\d{2}:\d{2}.\d{9})'
>      SPACE = r' '
>      FOO = r'some_regex'
>      BAR = r'some_regex'
>
>      regexes = {
>              'data_sent': re.compile("""
>                                          TIMESTAMP # Timestamp of our log message
>                                          SPACE
>                                          FOO # Some comment
>                                          SPACE
>                                      """, re.VERBOSE),
>              'data_received': re.compile("""
>                                          TIMESTAMP # Timestamp of our log message
>                                          SPACE
>                                          BAR # Some comment
>                                          SPACE
>                                      """, re.VERBOSE),
>                }
>
> Is there a way to use CONSTANTS (or at least re-use fragments of my regex), and also use re.VERBOSE so I can comment my regex?
>
You could do it like this:

     import re

     constants = {}
     constants['TIMESTAMP'] = r'(?P<timestamp>\d{2}:\d{2}:\d{2}.\d{9})'
     constants['SPACE'] = r'\ ' # Escape the space because it'll be in a 
VERBOSE regex.
     constants['FOO'] = r'some_regex'
     constants['BAR'] = r'some_regex'

     regexes = {
             'data_sent': re.compile("""
                                         {TIMESTAMP} # Timestamp of our 
log message
                                         {SPACE}
                                         {FOO} # Some comment
                                         {SPACE}
                                     """.format(**constants), re.VERBOSE),
             'data_received': re.compile("""
                                         {TIMESTAMP} # Timestamp of our 
log message
                                         {SPACE}
                                         {BAR} # Some comment
                                         {SPACE}
                                     """.format(**constants), re.VERBOSE),
               }