Question

I have the file called mda_bk-adds-gro.inp:

# -*- mode:python -*-
0.5, 0.5, 0.5, walp_fixed.gro
0.5, 0.5, 0.4, walp.gro

I think I’ll read the numbers and the the word separately. I’ve succeded in parsing the numbers:

loadtxt('mda_bk-adds-gro.inp', comments='#', delimiter=',', usecols=(0,1,2))

But can’t read in just words:

loadtxt('mda_bk-adds-gro.inp', comments='#', delimiter=',', dtype=[('fileName', '|S100')], usecols=(3))

it gives an error:

 TypeError: 'int' object is not iterable

So my question is – how do I read the forth column with loadtxt provided the column is str?

Answer 1

You get the TypeError because (3) is not a tuple, but just a parenthesized int-typed expression. Try usecols=(3,) instead.

See the comments at this issue for an explanation why this is so.