Short circuting

[Robert Kern]

On 1/21/11 5:33 PM, Ed Connell wrote:
> Hi,
>
> Consider the following please:  (re_section, re_name, etc are previously
> compiled patterns)
>
>                         result1 = re_section.search(line);
>                         result2 = re_name.search(line);
>                         result3 = re_data1.search(line);
>                         result4 = re_data2.search(line);
>
>                         if result1:
>                                 last_section = result1.group()[18:-5]
>                         elif result2:
>                                 last_name = result2.group(0)[6:-1]
>                         elif result3:
>                                 data[last_section] = {last_name:
> result3.group()[13:-5]}
>                         elif result4:
>                                 data[last_section] = {last_name:
> result4.group()[17:-5]}
>
> It gets my goat to have to obtain all resultx when I just want the first that is
> not None.  (In theory, the number of results can be much longer.)  I can think
> of alternatives (raising exceptions), but they all use deep indenting.

parsers = [
   ('section', re_section, lambda r: r.group()[18:-5]),
   ('name', re_name, lambda r: r.group()[6:-1]),
   ('data1', re_data1, lambda r: r.group()[13:-5]),
   ('data2', re_data2, lambda r: r.group()[17:-5]),
]

data = {}

for line in lines:
     values = {}
     for key, regex, extract in parsers:
         m = regex.search(line)
         if m is not None:
             values[key] = extract(m)
             break
     if 'data1' in values:
         data[values['section']] = {values['name']: values['data1']}
     elif 'data2' in values:
         data[values['section']] = {values['name']: values['data2']}

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco