Little direction please Python MySQL

len lsumnler at gmail.com
Mon Nov 17 16:56:21 CET 2008


On Nov 17, 5:52 am, Tim Chase <python.l... at tim.thechases.com> wrote:
> >> Files are fixed format no field delimiters, fields are position and
> >> length records are terminated by newline.
>
> > Assuming no COMPUTATIONAL fields, it should be easy enough to split each line up into fixed-length pieces, e.g. assuming a simple example
>
> >     01 Sample-Record.
> >       02 Field-1 pic XXX.
> >       02 Field-2 pic XXXX.
> >       02 Field-3 pic XXXXX.
>
> > then a Python sequence that read one line's worth of fields might be
>
> >     line = infile.read()
> >     (field_1, field_2, field_3) = (line[0:3], line[3:7], line[7:12])
>
> A recent posting on the list offered an elegant solution to this
> with a function something like
>
>    def splitter(s, *lens):
>      offset = 0
>      pieces = []
>      for length in lens:
>        pieces.append(s[offset:offset+length])
>        offset += length
>      return pieces
>
> which could then be used to simplify that to
>
>    (f1, f1, f3) = splitter(line, 3, 4, 5)
>
> It may not be quite so significant with just 3 items, but the OP
> mentioned having a large number of items in each record.  One
> could even use something like a mapping for this.  Something like:
>
>    field_lens = [
>      ("field1", 3),
>      ("field2", 4),
>      ("field3", 5),
>      # stacks more
>      ]
>    fields = dict(zip(
>      (name for name, _ in field_lens),
>      splitter(line, *[length for _, length in field_lens])
>      ))
>    something = "Whatever %s you want" % fields["field2"]
>
> If you like this method, you can even make a more targeted
> splitter() function and add some function mappings like
>
>    field_lens = [ # somewhat similar to your Cobol masks
>      ("field1", 3, str),
>      ("field2", 4, int),
>      ("field3", 5, float),
>      ("field4", 17, lambda s: s.strip().upper() ),
>      # stacks more
>      ]
>
>    def splitter(s, field_lens):
>      pieces = {}
>      offset = 0
>      for name, length, fn in field_lens:
>        pieces[name] = fn(s[offset:offset+length])
>        offset += length
>      return pieces
>
>    bits = splitter(line), field_lens)
>    # do addition of int+float rather than string concat
>    print bits["field2"] + bits["field3"]
>
> -tkc

Thank for your reply.  I will have to study your code and
see if I can inprove mine.

Len



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