Prev: Decimal problem
Next: MySQLdb problems with named pipe connection on Windows 7?
From: Anthony Papillion on 10 Jun 2010 16:47
Someone helped me with some code yesterday and I'm trying to
understand it. The way they wrote it was

subjects = (info[2] for info in items)

Perhaps I'm not truly understanding what this does. Does this do
anything different than if I wrote

for info[2] in items
subject = info[2]

Thanks!
Anthony
From: Emile van Sebille on 10 Jun 2010 17:19
On 6/10/2010 1:47 PM Anthony Papillion said...
> Someone helped me with some code yesterday and I'm trying to
> understand it. The way they wrote it was
>
> subjects = (info[2] for info in items)
>
> Perhaps I'm not truly understanding what this does. Does this do
> anything different than if I wrote
>
> for info[2] in items
> subject = info[2]
>

more like:

result = []
for info in items:
result.append(info[2])

subjects =iter(result)

Emile

From: Thomas Jollans on 10 Jun 2010 17:22
On 06/10/2010 10:47 PM, Anthony Papillion wrote:
> Someone helped me with some code yesterday and I'm trying to
> understand it. The way they wrote it was
>
> subjects = (info[2] for info in items)

This is a generator expression, and it creates a generator object. If
you loop over it (subjects), you will get all the subjects (or whatever
info[2] is), one by one.

>
> Perhaps I'm not truly understanding what this does. Does this do
> anything different than if I wrote
>
> for info[2] in items
> subject = info[2]

These two snippets do the same thing:

# No. 1.
subjects = (info[2] for info in items)
for subject in subjects:
print (subject)

# No. 2.
for info in items:
subject = info[2]
print (subject)


However, you could also pass the subjects variable to another function
and have it iterate over them - that's something that the simple loop
can't do just like that.

>
> Thanks!
> Anthony

From: Anthony Papillion on 10 Jun 2010 18:13
Thank you Emile and Thomas! I appreciate the help. MUCH clearer now.
From: Martin on 10 Jun 2010 18:27
On Jun 10, 11:13 pm, Anthony Papillion <papill...(a)gmail.com> wrote:
> Thank you Emile and Thomas! I appreciate the help. MUCH clearer now.

Also at a guess I think perhaps you wrote the syntax slightly wrong
(square brackets)...you might want to look up "list comprehension"

Martin
 |  Next  |  Last
Pages: 1 2
Prev: Decimal problem
Next: MySQLdb problems with named pipe connection on Windows 7?