[Tutor] List comprehensions
Dinesh B Vadhia
dineshbvadhia at hotmail.com
Thu Apr 10 08:15:44 CEST 2008
Now, N = 20 to 150 is not a lot (for a for loop) but this process is performed each time the user enters a character. Plus, there will be thousands (possibly more) users at a time. There is also the searching of the >10,000 string items using the entered character. All of this adds up in terms of performance.
I haven't done any profiling yet as we are still building the system but it seemed sensible that replacing the for loop with a built-in would help. Maybe not?
Hope that helps.
----- Original Message -----
From: Kent Johnson
To: Dinesh B Vadhia
Cc: tutor at python.org
Sent: Wednesday, April 09, 2008 1:48 PM
Subject: Re: [Tutor] List comprehensions
Dinesh B Vadhia wrote:
> Here is a for loop operating on a list of string items:
> data = ["string 1", "string 2", "string 3", "string 4", "string 5",
> "string 6", "string 7", "string 8", "string 9", "string 10", "string 11"]
> result = ""
> for item in data:
> result = <some operation on> item
> print result
> I want to replace the for loop with another structure to improve
> performance (as the data list will contain >10,000 string items]. At
> each iteration of the for loop the result is printed (in fact, the
> result is sent from the server to a browser one result line at a time)
Any savings you have from optimizing this loop will be completely
swamped by the network time. Why do you think this is a bottleneck?
You could use
[ sys.stdout.write(some operation on item) for item in data ]
but I consider this bad style and I seriously doubt you will see any
difference in performance.
> The for loop will be called continuously and this is another reason to
> look for a potentially better structure preferably a built-in.
What do you mean 'called continuously'?
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Tutor