Python help for a C++ programmer

[Bruno Desthuilliers]

mlimber a écrit :
> I'm writing a text processing program to process some survey results.
> I'm familiar with C++ and could write it in that, but I thought I'd
> try out Python. I've got a handle on the file I/O and regular
> expression processing,

FWIW, and depending on your text format, there may be better solutions 
than regexps.

> but I'm wondering about building my array of
> classes (I'd probably use a struct in C++ since there are no methods,
> just data).

If you have no methods and you're sure you won't have no methods, then 
just use a dict (name-indexed record) or a tuple (position-indexed record).

> I want something like (C++ code):
> 
>  struct Response
>  {
>    std::string name;
>    int age;
>    int iData[ 10 ];
>    std::string sData;
>  };
> 
>  // Prototype
>  void Process( const std::vector<Response>& );
> 
>  int main()
>  {
>    std::vector<Response> responses;
> 
>    while( /* not end of file */ )
>    {
>      Response r;
> 
>      // Fill struct from file
>      r.name = /* get the data from the file */;
>      r.age = /* ... */;
>      r.iData[0] = /* ... */;
>      // ...
>      r.sData = /* ... */;
>      responses.push_back( r );
>    }
> 
>     // Do some processing on the responses
>     Process( responses );
>  }
> 
> What is the preferred way to do this sort of thing in Python?

# assuming you're using a line-oriented format, and not
# worrying about exception handling etc...

def extract(line):
    data = dict()
    data['name'] = # get the name
    data['age'] = # get the age
    data['data'] = # etc...
    return data


def process(responses):
   # code here

if name == '__main__':
     import sys
     path = sys.argv[1]
     responses = [extract(line) for line in open(path)]
     process(response)

If you have a very huge dataset, you may want to either use tuples 
instead of dicts (less overhead) and/or use a more stream-oriented 
approach using generators - if applyable of course (that is, if you 
don't need to extract all results before processing)

HTH