Access first element in a os.scandir

Question

I am using os.scandir for getting the list of files in a folder:

img_list2 = os.scandir('/home/shared/test')

I want to get the first element.

I am trying img_list2.next()

>>> img_list2.next()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'posix.ScandirIterator' object has no attribute 'next'

So I tried:

>>> filt = list(img_list2)
>>> type(filt)
<class 'list'>
>>> globals()['filt']
[<DirEntry 'panaroma00010.jpg'>, <DirEntry 'panaroma00014.jpg'>, <DirEntry 'panaroma00004.jpg'>, <DirEntry 'panaroma00013.jpg'>, <DirEntry 'panaroma00007.jpg'>, <DirEntry 'panaroma00011.jpg'>, <DirEntry 'panaroma00012.jpg'>, <DirEntry 'panaroma00006.jpg'>, <DirEntry 'panaroma00009.jpg'>, <DirEntry 'panaroma00001.jpg'>, <DirEntry 'panaroma00003.jpg'>, <DirEntry 'panaroma00005.jpg'>, <DirEntry 'panaroma00002.jpg'>, <DirEntry 'panaroma00008.jpg'>]
>>> filt[1]
<DirEntry 'panaroma00014.jpg'>
>>>

So just like in list we can get the first element value, can we get it from os.scandir?

In addition to the answers below, here is the docs for Iterator in Python 3: https://docs.python.org/3/library/stdtypes.html#iterator-types. It says that Iterators only have the 'magic' functions `__iter__` and `__next__`. — Hubert Grzeskowiak, Sep 13 '16 at 14:19

Dimitris Fasarakis Hilliard · Accepted Answer · 2016-09-13T14:23:59.740

6

os.scandir() returns an iterator containing the directory entries for a given path, see help(os.scandir):

scandir(...)
    scandir(path='.') -> iterator of DirEntry objects for given path

To get a value from it call the built-in next on it:

next(img_list2)

This will return values from the iterator until it is exhausted (and StopIteration is raised).

You can also wrap it in a list call which create a list out of all entries and make it indexable but if you only require the first element that is overkill.

iterator.next() was removed as of Python 3.0 with PEP 3114; a dunder iterator.__next__() method replaced it along with the built-in next() that calls it.

edited Sep 13 '16 at 14:23

answered Sep 13 '16 at 14:17

Dimitris Fasarakis Hilliard

150,925
31
268
253

1

how to make a list with indexable entries – Santhosh Sep 13 '16 at 17:44
you necessarily must pass `img_list2` in `list()` and then you can index it, i.e `img_list3 = list(img_list2)`. – Dimitris Fasarakis Hilliard Sep 13 '16 at 17:51
Also in jinja2 code of my django project, i tried to use next(img_list2).path . its says error `django.template.exceptions.TemplateSyntaxError: Could not parse the remainder: '(img_list2).path' from 'next(img_list2).path' [13/Sep/2016 23:21:38] "GET /gallery/ HTTP/1.1" 500 130929 ` – Santhosh Sep 13 '16 at 17:53
Calling `list` on the iterator will make it a list, `list` objects don't have a path attribute. `list(img_list2)[0].path` would work, as would `next(img_list2).path`. – Dimitris Fasarakis Hilliard Sep 13 '16 at 17:54
No i am sending the interator img_list2 to the template. `return render(request,'blog/gallery.html', {'img_list2':img_list2})` – Santhosh Sep 13 '16 at 17:56
`next(img_list2).path` is not working when used in the jinja code in my html template – Santhosh Sep 13 '16 at 17:57
I can't see the code so I can't reason as to why that happens; I'd suggest you ask another question. – Dimitris Fasarakis Hilliard Sep 13 '16 at 17:58
http://stackoverflow.com/questions/39476401/django-pythons-os-scandir-next-method-not-working-inside-jinja2-code (added as new question) – Santhosh Sep 13 '16 at 18:06

score 1 · Answer 2 · answered Sep 13 '16 at 14:16

1

next() would give you the next item from the img_list2 iterator:

next(img_list2)

answered Sep 13 '16 at 14:16

alecxe

462,703
120
1,088
1,195

Access first element in a os.scandir

2 Answers2