Extracting values from text file

[Mirco Wahab]

Thus spoke Dennis Lee Bieber (on 2006-06-18 06:29):

> On Sun, 18 Jun 2006 03:12:23 +0200, Mirco Wahab
> <wahab at chemie.uni-halle.de> declaimed the following in comp.lang.python:
>> - you have to explicitly instantiate a dictionary value
>>   (with 0) if/before you want in-place add to it (why is that?)
> Uhm... Not quite...
> ...
> dict.get(key, default)
>
> returns the value associated by key, IFF key exists in the
> dictionary, otherwise it returns the value defined for default.

Thanks, Dennis, for your help on this part I bragged about.

Now the extractor loop, according to your suggestion, can
be written shorter:

for rule in filter:
    k = re.search(r'\((.+)\)', rule)         # pull out variable names ->k
    if k.group(1):                           # pull their values from text
        varname[k.group(1)] = varname.get(k.group(1), 0) + float( \
            re.search( re.sub(r'\((.+)\)', varscanner, rule),     \
                       example ).group(1)  ) # use regex in modified 'rule'

For the other issue I stumbled upon:

- no DWIM-ism (do what I mean) on 'value' addition

    a  = '1'
    a += '1.1111'
    print a

 will print
    11.1111

and not 2.1111, as in 'dynamically typed', 'operator based' languages.
(maybe the lack of a simple string-concatenation operator is the reason?)

  whereas:

    a  = '1'
    a += 1.1111
    print a

will fail magnificently. These thing would come handy
when working with text/table driven computations (as above)

How could one approach these things without needing to
get too explicitly about 'type conversions'
(Python is supposed to be 'dynamically typed'?).


Regards & thanks

Mirco