Re: [Pytables-users] =?utf-8?q?how_to_modify_a_single_cell_into_an_ex?= =?utf-8?q?isting=09table=3F?=

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

Hi Luca,

A Monday 07 January 2008, Ivan Vilata i Balaguer escrigu=C3=A9:
> Luca Della Santina (el 2008-01-07 a les 11:16:25 +0100) va dir::
> >[...]
> > I would like to modify the value contained in the third column of
> > the second row from the original value of 4 to 5 but couldn't find
> > a quick way to do it inside the pytables manual.
> >
> > In first stance i tried to:
> > mytable[1][2] =3D 5
> > mytable.flush()
> >
> > but in this way the new value is not written into the table (even
> > if no errors were reported).

This is because you should understand what's going on under the hood. =20
When you call mytable[1], this returns a row of the table as a NumPy=20
scalar (of 'void' type), and hence mytable[1][2] will set the 3rd=20
field of such (temporal) scalar.  So, the result is that your code=20
won't do nothing.

> ``Table.modifyColumn()`` is your friend::
>
>     mytable.modifyColumn(start=3D1, colname=3D'name_of_field2',
> column=3D[5]) mytable.flush()

You can use also the .cols accessor, which is slightly more confortable=20
IMO:

mytable.cols.name_of_field2[1] =3D 5

or, if you prefer using the field index instead of the name:

mytable.cols._f_col(mytable.colnames[2])[1] =3D 5

BTW, a Table.flush() is only needed when you append/modify the Table=20
using an iterator, so you don't need to issue it in this case.

Ciao,

=2D-=20
>0,0<   Francesc Altet =C2=A0 =C2=A0 http://www.carabos.com/
V   V   C=C3=A1rabos Coop. V. =C2=A0=C2=A0Enjoy Data
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