Thread: [Matplotlib-users] writing binary array to file

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What's the easiest way to write a Numeric array to a file?
Thanks!  --Randy

>>>>> "Randy" == Randy Heiland <he...@in...> writes:

    Randy> What's the easiest way to write a Numeric array to a file?

Easiest or best?

In the next release I've added load and save funcs for converting
arrays to and from ascii files.  But this is slow and generally lossy.

Best is to use the binary string operations tostring and fromstring

    from Numeric import fromstring, Float
    # write
    file('fname.out', 'wb').write(x.tostring())

    # read
    x = fromstring(file('fname.out', 'rb').read(), Float)

    #If data is MxN you'll need to reshape
    x.shape = M,N

Hope this help,
JDH

John Hunter wrote:
> Best is to use the binary string operations tostring and fromstring
> 
>     from Numeric import fromstring, Float
>     # write
>     file('fname.out', 'wb').write(x.tostring())
> 
>     # read
>     x = fromstring(file('fname.out', 'rb').read(), Float)
> 
>     #If data is MxN you'll need to reshape
>     x.shape = M,N
> 
> Hope this help,
> JDH
> 

Note that numarray has a tofile method and a fromfile function
to do this without going through the copying required by tostring
and fromstring. Like those, it also doesn't save any shape or
type info in the file.

Perry

Thanks much John & Perry!  Part of my confusion was the fact that I'm
using numarray on my laptop/Windows and Numeric on Linux... and I was in
a hurry... and general ignorance.  Anyway, thanks again.

Randy

> -----Original Message-----
> From: Perry Greenfield [mailto:pe...@st...]
> Sent: Thursday, April 08, 2004 1:48 PM
> To: John Hunter; Randy Heiland
> Cc: mat...@li...
> Subject: RE: [Matplotlib-users] writing binary array to file
> 
> John Hunter wrote:
> > Best is to use the binary string operations tostring and fromstring
> >
> >     from Numeric import fromstring, Float
> >     # write
> >     file('fname.out', 'wb').write(x.tostring())
> >
> >     # read
> >     x = fromstring(file('fname.out', 'rb').read(), Float)
> >
> >     #If data is MxN you'll need to reshape
> >     x.shape = M,N
> >
> > Hope this help,
> > JDH
> >
> 
> Note that numarray has a tofile method and a fromfile function
> to do this without going through the copying required by tostring
> and fromstring. Like those, it also doesn't save any shape or
> type info in the file.
> 
> Perry
> 

----- Original Message ----- 
From: "Perry Greenfield" <pe...@st...>
To: "John Hunter" <jdh...@ni...>; "Randy Heiland"
<he...@in...>
Cc: <mat...@li...>
Sent: Thursday, April 08, 2004 10:47 PM
Subject: RE: [Matplotlib-users] writing binary array to file

> John Hunter wrote:
> > Best is to use the binary string operations tostring and fromstring
> >
> >     from Numeric import fromstring, Float
> >     # write
> >     file('fname.out', 'wb').write(x.tostring())
> >
> >     # read
> >     x = fromstring(file('fname.out', 'rb').read(), Float)
> >
> >     #If data is MxN you'll need to reshape
> >     x.shape = M,N
> >
> > Hope this help,
> > JDH
> >
>
> Note that numarray has a tofile method and a fromfile function
> to do this without going through the copying required by tostring
> and fromstring. Like those, it also doesn't save any shape or
Moreover tostring() and fromstring() are deprecated iirc, because you can
convert arrays from and to strings by StringIO.
> type info in the file.
>
> Perry
>
>
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Eugeni Doljenko writes:
> > John Hunter wrote:
> > > Best is to use the binary string operations tostring and fromstring
> > >
> > >     from Numeric import fromstring, Float
> > >     # write
> > >     file('fname.out', 'wb').write(x.tostring())
> > >
> > >     # read
> > >     x = fromstring(file('fname.out', 'rb').read(), Float)
> > >
> > >     #If data is MxN you'll need to reshape
> > >     x.shape = M,N
> > >
> > > Hope this help,
> > > JDH
> > >
> >
> > Note that numarray has a tofile method and a fromfile function
> > to do this without going through the copying required by tostring
> > and fromstring. Like those, it also doesn't save any shape or
> Moreover tostring() and fromstring() are deprecated iirc, because you can
> convert arrays from and to strings by StringIO.
>
I just noticed this recently. It isn't the case that tostring and
fromstring are deprecated for numarray. I just wanted to clarify.

Perry 

If you're not intereste in creating a text file,

The best way to go, is with pickle.dump and pickle.load

Check the python docs about them.

cheers,

Fl=E1vio

On Thu, 2004-04-08 at 17:38, Randy Heiland wrote:

> What's the easiest way to write a Numeric array to a file?
> Thanks!  --Randy
>=20
>=20
>=20
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