[mne-python] strange behavior of raw.save()

✉️ Mailing List Archive (read-only)
1

Hi all,

on saving a raw file using the instance method save() I get the
following error message.

http://pastebin.com/g66H4svV

After that the file is not readable anymore ( the same error message
will appear as Raw.__init__() is called. )

If I use an alternative file name this does not happen.

a) what is the reason for that / what does it actually tell, and

b) shouldn't that rather throw an exception than messing up the original file?

Cheers,
Denis

2

Hi Denis,

Are you by any chance saving the raw file to the same file from where
you read it? I.e., something like

raw = Raw('test_raw.fif')
..
raw.save('test_raw.fif')

Unless you use preload=True, this won't work since raw.save() will read
from the file and at the same time overwrite it. We should add a check
such that it throws and exception with a explanatory error message if
one tries to do this.

Martin

3

Thanks Martin,

that must be it.
I actually I was testing a new command line tool of mine for mass riff
export / augmentation / conversion
And in one of the use cases I simply wanted to change the info
structure without loading the data.
So this means I can either preload the data or work around it by e.g.
iterative renaming.

To prevent users from tnings like that one could add something like

raw.save(fname)

(...)

if fname == self.raw.info['filename'] and not self.preload:
    raise ValueError("Invalid operation "
                            "Either load data or use alternative file name")

Wdyt?

Cheers,
Denis

2012/9/8 Martin Luessi <mluessi at nmr.mgh.harvard.edu>:

4

Ok, I tried the following:

I added

if fname == self.info['filename'] and not hasattr(self,'_data'):
            raise ValueError('Invalid operation. Either read data with preload '
                                    'option or use alternative file name')

to Raw.save

Hower, in case the data is preloaded the file still breaks...

2012/9/8 Denis-Alexander Engemann <d.engemann at fz-juelich.de>:

5

Ok. self._preload

2012/9/9 Denis-Alexander Engemann <d.engemann at fz-juelich.de>:

6

Ok, self._data == True or self._preodaded == True does not make a difference.

Is it at all possible to write make a ras.save using the identical fid?
Otherwise we should just add:

if fname == self.info['filename']:
            raise RuntimeError('Invalid operation. Use an alternative
file name')

2012/9/9 Denis-Alexander Engemann <d.engemann at fz-juelich.de>