[Numpy-discussion] "formstring()" in place?

Chris Barker cbarker at jps.net
Fri Nov 3 14:40:45 EST 2000

Janko Hauser wrote:
> Use the numpyio module from Travis. With this it should be possible to
> read the data directly and do any typecode conversion you want
> with. It has fread and fwrite functions, and it can be used with any
> NumPy type like Int0 in your case. It's part of the signaltools
> package.
> http://oliphant.netpedia.net/signaltools_0.5.2.tar.gz

I've downloaded it , and it looks pretty handy. It does include a
byteswap-in-place, which I need. What is not clear to me from the
minimal docs is whether I can read file set up like:
long long char long long char ....
and have it put the longs into one array, and the chars into another.

Also, It wasn't clear whether I could put use it to read a file that has
already been opened, starting at the file's current position. I am
working with a file that has a text header, so I can't just suck in the
whole thing until I've parsed out the header.

I can figure out the answer to these questions with some reding of the
source, but it wasn't obvious at first glance, so it would be great if
someone knows the answer off the top of there head. Travis?

By the way, there seem to be a few methods that produce a copy, rather
than doing things in place, where it seems more intuitive to do it in
place. byteswapped() and astype() come to mind. With byteswapped, I
imagine it's rare that you would want to keep a copy around. With astype
it would also be rare to keep a copy around, but since it changes the
size of the array, I imagine it would be a lot harder to code as an
in-place operation. Is there a reason these operations are not available
in-place? or is it just that no one has seen enough of a need to write
the code.


Christopher Barker,
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