Difference between tempfile and spooled tempfile?

[Steve Howell]

On Apr 5, 8:10 am, Steve Howell <showel... at yahoo.com> wrote:
> On Apr 5, 7:50 am, "Alex van der Spek" <zd... at xs4all.nl> wrote:
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> > I do not understand why the spooled write gives an error. See below.
> > The normal tempfile works just fine. They are supposed to behave equal?
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> > All insight you can provide is welcome.
> > Alex van der Spek
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> > +++++++++++++++++++++++++++++++++++++++++++++++++
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> > Python 2.7.1 (r271:86832, Nov 27 2010, 18:30:46) [MSC v.1500 32 bit (Intel)]
> > on win32
> > Type "copyright", "credits" or "license()" for more information.
>
> > >>> import array
> > >>> import tempfile
> > >>> stf = tempfile.SpooledTemporaryFile(max_size=1024)
> > >>> ptf = tempfile.TemporaryFile()
> > >>> fff = [float(x) for x in range(2048)]
> > >>> ffa = array.array('f',fff)
> > >>> ptf.write(ffa)
> > >>> stf.write(ffa)
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> > Traceback (most recent call last):
> >   File "<pyshell#7>", line 1, in <module>
> >     stf.write(ffa)
> >   File "C:\Python27\lib\tempfile.py", line 595, in write
> >     rv = file.write(s)
> > TypeError: must be string or read-only character buffer, not array.array
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> I think the docs are slightly misleading.  While SpooledTemporaryFile
> allows you to write(), it's more finicky about serializing arrays,
> hence the error message.
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> If you look under the hood, you'll see that it's mostly a limitation
> of StringIO.
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> http://hg.python.org/cpython/file/2.7/Lib/tempfile.py
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>    494     """Temporary file wrapper, specialized to switch from
>    495     StringIO to a real file when it exceeds a certain size or
>    496     when a fileno is needed.
>    497     """
>    498     _rolled = False
>    499
>    500     def __init__(self, max_size=0, mode='w+b', bufsize=-1,
>    501                  suffix="", prefix=template, dir=None):
>    502         self._file = _StringIO()
>    503         self._max_size = max_size
>    504         self._rolled = False
>    505         self._TemporaryFileArgs = (mode, bufsize, suffix,
> prefix, dir)
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> (See line 502.)
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>    600     def write(self, s):
>    601         file = self._file
>    602         rv = file.write(s)
>    603         self._check(file)
>    604         return rv
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> (See line 602.)
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> I'm looking at a slightly different version of the module than you,
> but hopefully you get the idea.

P.S. The problems the OP is encountering may be a side effect of this
bug:

http://bugs.python.org/issue1730114