On Sat, 26 Jan 2013, Pietro Battiston wrote:
> I love Gretl's "foreign" code blocks capability, and would love even
> more the possibility of using Python in them, which was at some time
> suggested as easy to implement.
Yes, quite easy. In fact, so easy that Python support is now
in gretl CVS and the snapshots for Windows and OS X. Here's a
trivial example:
Cool. Thanks. Is there any way to browse this changeset in the repository through the web interface? Git/github has eroded all of my other version control skills.
<hansl>
matrix M = I(5)
mwrite(M, "@dotdir/pytest.mat")
foreign language=python
G = gretl_loadmat('pytest.mat')
G *= 5
gretl_export(G, 'pyout.mat')
end foreign
matrix pymat = mread("@dotdir/pyout.mat")
print pymat
</hansl>
When you call python via gretl's "foreign" mechanism you have
three gretl_ functions available:
gretl_loadmat(): reads a matrix, as written by gretl's
mwrite(), from gretl's per-user dotdir.
gretl_export(): writes a matrix, readable via gretl's mread(),
into the gretl dotdir.
gretl_dotdir(): in case you need it, gives the dotdir path.
When python is invoked via gretl, one thing that happens
automatically is:
import numpy as np
This is in part because numpy is needed for the implementation
of gretl_loadmat and gretl_export, which use np.loadtxt and
np.savetxt respectively. I'm not a python person, but I
suspect that some users might not like the "import" statement
as I have it. Comments welcome.
This is the preferred import convention for numpy, so there's no reason to not like it from a style standpoint. Are you concerned with this or the importing the kitchen sink aspect?
Related question: in Python, as in R, Octave and Ox, the
"dotdir" business (which ensures we have a user-writable and
gretl-findable location) is hidden from the matrix read/write
functions, but on the gretl end you have to use @dotdir
explicitly with mwrite and mread when interfacing with
"foreign".
Any sale for a pair of gretl functions mexport() and mimport()
which handle the prepending of dotdir automatically?
Allin Cottrell