import re
# python REGXP: {{{
# . matches any char                (include end-of-line(EOL) if re.S is on)
#                                               vim:. (always NO EOL)
# ^ $ matches start/end of string   (include EOL start/end if re.M is on)
# *  matches 0+
# +  matches 1+                                 vim: \+
# ?  matches 0 or 1                             vim: \? \=
# {} matches numbers                            vim: \{}
# *? +? ??  {}? matches the minimal             vim: \{-}
# \ escape
# [] character set
# () group
# (?<!...) no preceding                         vim: \@<!
# (?<=...) with preceding                       vim: \@<=
# (?!...)  no following                         vim: \@!
# (?=...)  with following                       vim: \@=
# (?:...)  ignore group number                  vim: \%(\)
# (?P<NAME>...) define the group 'NAME'
# (?P=name)  match the group 'name'
# (?(id/name)yes-pattern|no-pattern)
#       match the yes-pattern if the group id/name exists      
# (?iLmsux) re option:ignore/locale/multiline/dot2all/unicode/verbose
# 
# NOTE 
# MODULE:
# re.compile() Compile a regular expression pattern into a regular expression object
# {{{ e.g.
# prog = re.compile(pattern)
# result = prog.match(string)
# is equivalent to:
# result = re.match(pattern, string)
# }}}
# finditer()  returns iterable
# findall()   returns string list
# match(string,[pos,[endpos]])     match object match with whole ptn
# search(string,[pos,[endpos]])    match object if ptn exists in it
# split(ptn,str)     returns string list    vim:split(str,ptn)
# sub(ptn,rpl,str,flag)                     vim:substiture(str,ptn,rpl,flag)
# escape()    Return string with all non-alphanumerics backslashed
# 
# Regular Object:
# groups        number of groups
# pattern       compiled pattern
# flags         compiled flag
#
# Match Object:
# expand(tmpl)    expand character '\1','\n' in tmpl
# group()       return subgroup string 0:entire match 1,2...:subgroup
# groups()      return subgroup tuple
# groupdict()   return subgroup dict with group which have NAME
# start() end() return idx of the group in whole string.
# span()        return (start,end) tuple
# pos           the pos passed to search()/match() 
# endpos        the endpos passed to search()/match() 
# string        the string passed to search()/match() 
# lastgroup     last matched group
# re            thre regular object produce this match object
# 
# ERRORS:
# XXX look-behind requires fixed-width pattern
# (?<![0-9a-fA-F]|0[xX]) is wrong!! 
# (?<![0-9a-fA-F])|(?<!0[xX]) is wrong
#  (?<!([\w\#]))      final use
# XXX unbalanced parentheses
# use raw text r'''\(......\) '''
# or escape twice '\\(......\\)' 
# }}}
 

vim 下的\s 和python 的\s 不同

python 的\s 是[ \t\n\r\f\v]

vim 的 \s 是[ \t ]