[Tutor] curious struct problem

[Bob Gailer]

Marcus Goldfish wrote:
> I'm trying to read a binary file using struct.  This code works 
> interactively in the IPython shell, but not as a function invoked from 
> a command line (Windows).  

> Can someone point out my error?  Thanks!
Not without more information:
  What are you entering on the command line?
  What do you enter in the IPython shell to run the function?

>
> import struct
>
> def demux(filename, channel, nchannels):
>    "Demultiplexes a stream of shorts (signed int16) from a file."
>    fmt = str(nchannels) + 'h'
>    sz = struct.calcsize(fmt)
>
>    infile = open(fname, 'rb')
>    chunk = infile.read(sz)
>    while chunk:
>       x = struct.unpack(fmt, chunk)
>       chunk = infile.read(sz)
>    infile.close()
>
> #struct.error: unpack str size does no match format
>
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-- 
Bob Gailer
510-978-4454