multiple pattern regular expression

[Arnaud Delobelle]

Chris Henry <chrishenry.ni at gmail.com> writes:

> On Apr 25, 8:37 pm, Arnaud Delobelle <arno... at googlemail.com> wrote:
>> micron_make <micro_pass... at yahoo.com> writes:
>> > I am trying to parse a file whose contents are :
>>
>> > parameter=current
>> > max=5A
>> > min=2A
> [snip]
>> If every line of the file is of the form name=value, then regexps are
>> indeed not needed.  You could do something like that.
>>
>> params = {}
>> for line in file:
>>     name, value = line.strip().split('=', 2)
                                             ^ 1, obviously!
>>     params[name] = value
>>
>> (untested)
>> Then params should be the dictionary you want.
>>
> I'm also interested in this problem. While this solution works, I'm
> looking for solution that will also check whether the parameter name/
> value is of a certain pattern (these patterns may be different, e.g.
> paramA, paramB, paramC may take integers value, while paramD may take
> true/false). Is there a way to do this easily?
>
> I'm new to Python and the solution I can think off involve a loop over
> a switch (a dictionary with name->function mapping). Is there other,
> more elegant solution?

Sounds good to me.

E.g.

def boolean(x):
    if x == 'true':
        return True
    elif x == 'false'
        return False
    else:
        raise ValueError("Invalid boolean: '%s'" % x)

paramtypes = { 'paramA': int, ..., 'paramD': boolean }

#Then

for line in file:
    line = line.strip()
    if not line: continue
    name, value = line.split('=', 1)
    if name in paramtypes:
        try:
            value = paramtypes[name](value)
        except ValueError, e:
            # handle the error
            value = e
    else:
        # What to do for untyped parameters
        pass
    params[name] = value

-- 
Arnaud