python dictionary question

Question

All,

This is the request from the template that i get

u'subjects': [u'7', u'4', u'5', u'3', u'2', u'1']

In my views how to extract the values like 7 4 5 3 2 1

How do i extract the above sequence from

new_subjects=request.POST.get('subjects')

Thanks.

Answer 1

Something like the following:

try:
    int_subjects = [int(x) for x in new_subjects]
except ValueError:
    #There was an error parsing.

Answer 2

try:
    int_subjects = map(int, new_subjects)
except ValueError:
    #There was an error parsing.

Using timeit in ipython shows that map is slightly faster than the comprehension in this case

In [99]: timeit map(int,new_subjects)
100000 loops, best of 3: 7.81 µs per loop

In [100]: timeit [int(x) for x in new_subjects]
100000 loops, best of 3: 8.8 µs per loop

Answer 3

request.POST is an instance of QueryDict which have a method named getlist that returns a list of values for the given key.

Example:

>>> new_subjects = request.POST.getlist('subjects')
>>> print new_subjects
[u'7', u'4', u'5', u'3', u'2', u'1']

See gnibbler's response for converting the list items to integers.

Answer 4

let's see: list comprehension, map...

...the generator version is missing:

In [3]: %timeit (int(x) for x in new_subjects)
1000000 loops, best of 3: 875 ns per loop

In [4]: %timeit map(int,new_subjects)
100000 loops, best of 3: 4.7 us per loop

benchmarking it like this is cheating though