'Return the positional index of column ``name``.
Parameters
name : str
column name
Returns
index : int
Positional index of column ``name``.
Examples
Create a table with three columns \'a\', \'b\' and \'c\'::
>>> t = Table([[1, 2, 3], [0.1, 0.2, 0.3], [\'x\', \'y\', \'z\']],
...           names=(\'a\', \'b\', \'c\'))
>>> print(t)
a   b   c
1 0.1   x
2 0.2   y
3 0.3   z
Get index of column \'b\' of the table::
>>> t.index_column(\'b\')
1'

def index_column(self, name):

    try:
        return self.colnames.index(name)
    except ValueError:
        raise ValueError(u'Column    {0}    does    not    exist'.format(name))
