Documentation, assignment in expression.

Tim Chase python.list at tim.thechases.com
Sun Mar 25 15:03:14 CEST 2012


On 03/25/12 07:18, Alexander Blinne wrote:
> I am not sure I understand your argument. The doc section states that
>
> " [...] in Python you’re forced to write this:
>
> while True:
>      line = f.readline()
>      if not line:
>          break
>      ... # do something with line".
>
> That simply isn't true as one can simply write:
>
> for line in f:
> 	#do stuff

I think the complaint was backed by a bad example.  Perhaps a DB 
example works better.  With assignment allowed in an evaluation, 
you'd be able to write

   while data = conn.fetchmany():
     for row in data:
       process(row)

whereas you have to write

   while True:
     data = conn.fetchmany()
     if not data: break
     for row in data:
       process(row)

Granted, this can be turned into an iterator with a yield, making 
the issue somewhat moot:

   def db_iter(conn, *args, **kwargs):
     while True:
       data = conn.fetchmany(rows, *args, **kwargs)
       if not data: break
       for row in data:
         yield row

   for row in db_iter(conn):
     proecss(row)

-tkc











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