Re: [Pytables-users] Modifying existing rows in a table?

[Francesc A. <fa...@ca...>]

Hi Norbert,

The Table.row object is only defined as a mean to allow fast appends to
Table objects, and it was designed to work only with this goal.

I agree with you in that allowing:

for row in mytable.iterrows():
    row['x'] =3D row['x'] + 0.5

would be nice, but the problem is that Row.__setitem__ only puts its value
in a buffer, that is intended to be written to disk afterwards.

An easy workaround would be defining a new class, say RowMod (for Row
Modification), so that its __setitem__ method would work as you want. Once
we have this, mytable.iterrows() would return instances of class RowMod,=20
not Row.

That way, the next should work:

row =3D mytable.row
for i in range(3):
    row['x'] =3D i
    row.append()
mytable.flush()

but also,

for row in mytable.iterrows():
    row['x'] =3D row['x'] + 0.5

Mmm, I'll think more on that, and if I find this feasible (and more
importantly, find the time), I'll try to implement that.

By the way, a good workaround for what you are trying for is:

for i in xrange(mytable.nrows):
    mytable.cols.x[i] =3D mytable.cols.x[i] + 0.5

Cheers,

A Dimarts 25 Gener 2005 15:51, Norbert Nemec va escriure:
> Hi there,
>
> i would have assumed that the following works:
> -------------------------
> #!/usr/bin/env python
>
> from tables import *
>
> file =3D openFile('tryout.h5','w')
>
> desc =3D {}
> desc['x'] =3D FloatCol()
>
> file.root.mytable =3D Table(desc)
> mytable =3D file.root.mytable
>
> row =3D mytable.row
> for i in range(3):
>     row['x'] =3D i
>     row.append()
> mytable.flush()
>
> for row in mytable.iterrows():
>     row['x'] =3D row['x'] + 0.5
> mytable.flush()
>
> for row in mytable.iterrows():
>     print row['x']
>
> file.close()
> -------------------------
>
> but obviously, the writing is completely ignored. Is this intuitive
> approach wrong? Is it just not implemented yet? Is there some other way t=
he
> same thing could be done?
>
> Ciao,
> Norbert

=2D-=20
>qo<   Francesc Altet =A0 =A0 http://www.carabos.com/
V =A0V   C=E1rabos Coop. V. =A0=A0Enjoy Data
 ""