[Numpy-discussion] example reading binary Fortran file

[Pradeep Jha]

Neil Martinsen-Burrell <nmb <at> wartburg.edu> writes:

> 
> On 2009-05-29 10:12 , David Froger wrote:
> > I think the FortranFile class is not intended to read arrays written
> > with the syntax 'write(11) array1, array2, array3'  (correct me if I'm
> > wrong).  This is the use in the laboratory where I'm currently
> > completing a phd.
> 
> You're half wrong.  FortranFile can read arrays written as above, but it 
> sees them as a single real array.  So, with the attached Fortran program::
> 
> In [1]: from fortranfile import FortranFile
> 
> In [2]: f = FortranFile('uxuyp.bin', endian='<') # Original bug was 
> incorrect byte order
> 
> In [3]: u = f.readReals()
> 
> In [4]: u.shape
> Out[4]: (20,)
> 
> In [5]: u
> Out[5]:
> array([ 101.,  111.,  102.,  112.,  103.,  113.,  104.,  114.,  105.,
>          115.,  201.,  211.,  202.,  212.,  203.,  213.,  204.,  214.,
>          205.,  215.], dtype=float32)
> 
> In [6]: ux = u[:10].reshape(2,5); uy = u[10:].reshape(2,5)
> 
> In [7]: p = f.readReals().reshape(2,5)
> 
> In [8]: ux, uy, p
> Out[8]:
> (array([[ 101.,  111.,  102.,  112.,  103.],
>         [ 113.,  104.,  114.,  105.,  115.]], dtype=float32),
>   array([[ 201.,  211.,  202.,  212.,  203.],
>         [ 213.,  204.,  214.,  205.,  215.]], dtype=float32),
>   array([[ 301.,  311.,  302.,  312.,  303.],
>         [ 313.,  304.,  314.,  305.,  315.]], dtype=float32))
> 
> What doesn't currently work is to have arrays of mixed types in the same 
> write statement, e.g.
> 
> integer :: index(10)
> real :: x(10,10)
> ...
> write(13) x, index
> 
> To address the original problem, I've changed the code to default to the 
> native byte-ordering (f.ENDIAN='@') and to be more informative about 
> what happened in the error.  In the latest version (attached):
> 
> In [1]: from fortranfile import FortranFile
> 
> In [2]: f = FortranFile('uxuyp.bin', endian='>') # incorrect endian-ness
> 
> In [3]: u = f.readReals()
> 
> IOError: Could not read enough data.  Wanted 1342177280 bytes, got 132
> 


Hello,

I am trying to read a fortran unformatted binary file with 
FortranFile as follows but I get an error.
-----------------------------------------
>>> from FortranFile import FortranFile
>>> f = FortranFile("vor_465.float",endian="<")
>>> u = f.readReals()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "FortranFile.py", line 193, in readReals
    data_str = self.readRecord()
  File "FortranFile.py", line 140, in readRecord
    data_str = self._read_exactly(l)
  File "FortranFile.py", line 124, in _read_exactly
    '  Wanted %d bytes, got %d.' % (num_bytes, l))
IOError: Could not read enough data.  
Wanted 1124054321 bytes, got 536870908.
------------------------------------------

My file, "vor_465.float" has the following size:
------------------------------------------
[pradeep@laptop ~]$ls -l vor_465.float 
-rwxr-xr-x  1 pradeep  staff  536870912 Feb 13 ***
-----------------------------------------

I am sure this file has data in the right format as 
when I read it using  fortran using the following command:

--------------------------------------------------
open (in_file_id,FILE="vor_465.float",form='unformatted',
         access='direct',recl=4*512*512*512)
read (in_file_id,rec=1) buffer
--------------------------------------------------

it works completely fine. This data contains single precision float 
values for a scalar over a cube with  512 points in each direction.

Any ideas?
Pradeep