[Tutor] quicker .strip?

[Lloyd Kvam]

Stryder wrote:

> Wow, completely surprised by the quick reply, thanks all!
> 
(snipped)
> Why the * with zip though?  It seems to be necessary to achieve the
> formatting I want, but I didn't notice any direct reference to it in the
> python23 doc.
> 
> -Stryder

zip is written to get multiple arguments, each of which is a sequence, e.g.:
	zip( (1,2,3), (4,5,6), (7,8,9) )

fetchall would return the above data like so:
	( (1,2,3), (4,5,6), (7,8,9) )
embedded in a tuple.

Python as some alternative syntax for passing parameters to functions.  If
you have a tuple that contains the positional arguments for a function, passing
the tuple with a preceding * causes the contents of the tuple to be mapped into
the positional args.

Similarly a dictionary passed with ** preceding it will map its contents to the
keyword parameters of a function.

These conventions allow you to easily program cases where the arguments for
functions originate in less conventional ways - such as you've just encountered
with fetchall and zip.

> 
> -----Original Message-----
> From: tutor-bounces at python.org [mailto:tutor-bounces at python.org] On
> Behalf Of Lloyd Kvam
> Sent: Friday, January 09, 2004 1:18 PM
> To: firephreek
> Cc: tutor at python.org
> Subject: Re: [Tutor] quicker .strip?
> 
> 
> fetchall returns a list of lists (well tuples, but you understand).
> Effectively it's a matrix.  Your data looks a little funny because each
> row is a single element.
> 
> I'd suggest:
> 
> ip = cursor.fetchall()
> for x in ip:	# row by row
> 	for alpha in x:	# column by column
> 		config=getConfig(alpha)  ##Custom function that uses
> httplib to
> 
> There's no need to convert the row to a string and remove the characters
> introduced by the conversion.  The IP address is already there as a
> string.
> 
> A cute coding trick for this case:
> 
> ip_list = zip(*cursor.fetchall())[0]
> for ip in ip_list:
> 	config =getConfig(ip)
> 
> While we usually think of zip as peeling of list members in parallel it
> is actually a matrix transpose function.  This converts the fetchall
> results from a list of rows to a list of columns.  Your ip addresses are
> the first
> (zeroth) column.
> 
> HTH
> 
> 
> Lloyd Kvam
> Venix Corp.
> 1 Court Street, Suite 378
> Lebanon, NH 03766-1358
> 
> voice:	603-653-8139
> fax:	801-459-9582
> 
> 
> _______________________________________________
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> 
> 

-- 
Lloyd Kvam
Venix Corp.
1 Court Street, Suite 378
Lebanon, NH 03766-1358

voice:	603-653-8139
fax:	801-459-9582