#27777: File object does not consistently open itself in context manager use
-----------------------------------------------+------------------------
Reporter: Raphael Gaschignard | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: 1.10
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-----------------------------------------------+------------------------
Django's {{{File}}} object has an open method that will reseek the file to
0, and re-open the file if necessary (after closure).
Unfortunately, the context manager does not automatically open a file. In
particular, {{{FieldFile}}} relies on implicit opening via the file
property to open a file, but caches the object internally. Since the
context manager for {{{File}}} closes the file after use, this means that
using the context manager twice in a row fails (since the file is not re-
opened).
{{{
class C(Model):
pdf = FileField(...)
c = C.objects.get()
with c.pdf as pdf: # file not opened yet
print(c.size) # pdf.size accesses pdf.file, which will implicitly
open the file
# file is closed at the end of a context manager
with c.pdf as pdf:
print(c.size) # pdf.size now uses cached file, which is already
closed!
}}}
I think it makes sense to have the context manager({{{__enter__}}}) call
{{{open}}} on the object, so that files can be used in multiple context
managers without having to to an open-ness check.
our current workaround is to check for closed-ness on all context manager
uses:
{{{
with c.pdf as pdf:
if pdf.closed():
pdf.open() # seeks the file to 0 and opens if necessary
# do "real" work
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/27777>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/047.7bb113c2fe8faffa4fbd45a3d42d5795%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.
