pytables-users

[Pytables-users] editing a row of a table

[Andrew S. <str...@as...>]

Hi,

Should I be able to do something like the following?

for row in table:
    row['y'] = row['x'] + 2

If so, how do I commit these changes to disk? table.flush() doesn't seem 
to work.

It seems like this simple example should be in the tutorial and the unit 
tests, but I can't find it anywhere. ("How to edit a row")  

Or maybe rows of tables can't be edited?

Cheers!
Andrew

Re: [Pytables-users] editing a row of a table

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

A Divendres 24 Desembre 2004 06:22, Andrew Straw va escriure:
> Should I be able to do something like the following?
>=20
> for row in table:
>     row['y'] =3D row['x'] + 2
>=20
> If so, how do I commit these changes to disk? table.flush() doesn't seem=
=20
> to work.

Well, you can do something like:=20

   # Modify field 'y'
   table.cols.y[:] =3D table.cols.x[:]+2
   # Modify rows 1 to the end with an stride of 2 in field 'y'
   table.cols.y[1::2] =3D table.cols.x[1::2]+2

Which is equivalent to:

   # Modify field 'y'
   table.modifyColumns(start=3D1, columns=3D[[table.cols.x[1]+2]], names=3D=
["y"])
   # Modify rows 1 to the end with an stride of 2 in field 'y'
   columns =3D numarray.records.fromarrays([table.cols.x[1::2]+2], formats=
=3D"i4")
   table.modifyColumns(start=3D1, step=3D2, columns=3Dcolumns, names=3D["y"=
])

[Example taken from the pytables user's manual (Column.__setitem__ section),
just slightly adapted to your example]

> It seems like this simple example should be in the tutorial and the unit=
=20
> tests, but I can't find it anywhere. ("How to edit a row") =20

Maybe I should improve the manual, most specially adding a tutorial for
value modification.

Cheers,

=2D-=20
=46rancesc Altet =A0   >qo< =A0 http://www.carabos.com/
C=E1rabos Coop. V. =A0 V =A0V =A0 Enjoy Data
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ""