[Tutor] Re: lists in re?

[Karl Pflästerer]

On  9 Sep 2003, Andreas Zwinkau <- andi at buxach.de wrote:

> If this gets more and more, i thought a dictionary would be the best way
> to define it in a obvious way. So this dict needs to be fed to the re
> module, but instead of processing each item, i wanted to re.compile it
> in one piece.

Did you think about writing it in a functional way?  I took the regexps
from one one your previous postings to write the example.

[lambda string, x=reg, y=exp: re.compile(x).sub(y, string)
 for (reg, exp) in
 [  # (regexp, expansion)
    ("''(.+)''", r"<it>\1</it>"), # italic
    (r"\*\*(.+)\*\*", r"<bold>\1</bold>"), #bold
    ("\[([\w \=\-\_\.]+)\]", r"<a href=\"\1\">\1</a>"), #link
    ("(?<=\n)\* (.*)\n", r"<ul><li>\1</li></ul>\n"), #list
    ("__(.+?)__", r"<u>\1</u>") # underline
    ]]

def wikinize (funs, stream):
    for fun in funs:
        stream = fun(stream)
    return stream


We do here mainly two things:

( 1) We build a list of anonymous functions.  Each function takes three
     parameters: the string to be altered, a regular expression and an
     expansion.  The regexp and the expansion are taken from a list of
     tuples (in each function they are bound to the correspondent values
     from the tuples).

( 2) We write a function which takes a list of functions (our previously
     build list) and a string.

here is an example

>>> s = "''abc''def**ghi**jkl[link]__underline__"
>>> flist =[lambda string, x=reg, y=exp: re.compile(x).sub(y, string)
...  for (reg, exp) in
...  [  # (regexp, expansion)
...     ("''(.+)''", r"<it>\1</it>"), # italic
...     (r"\*\*(.+)\*\*", r"<bold>\1</bold>"), #bold
...     ("\[([\w \=\-\_\.]+)\]", r"<a href=\"\1\">\1</a>"), #link
...     ("(?<=\n)\* (.*)\n", r"<ul><li>\1</li></ul>\n"), #list
...     ("__(.+?)__", r"<u>\1</u>") # underline
...     ]]
>>> wikinize(flist, s)
'<it>abc</it>def<bold>ghi</bold>jkl<a href=\\"link\\">link</a><u>underline</u>'
>>> 


If you want to add new regexps and their expansions you only have to
change one list.

   Karl
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