datascience.tables.Table.append_column

Table.append_column(label, values, formatter=None)[source]

Appends a column to the table or replaces a column.

__setitem__ is aliased to this method:

table.append_column('new_col', make_array(1, 2, 3)) is equivalent to table['new_col'] = make_array(1, 2, 3).

Args:

label (str): The label of the new column.

values (single value or list/array): If a single value, every

value in the new column is values.

If a list or array, the new column contains the values in values, which must be the same length as the table.

formatter (single formatter): Adds a formatter to the column being

appended. No formatter added by default.

Returns:

Original table with new or replaced column

Raises:
ValueError: If

  • label is not a string.

  • values is a list/array and does not have the same length as the number of rows in the table.

>>> table = Table().with_columns(
...     'letter', make_array('a', 'b', 'c', 'z'),
...     'count',  make_array(9, 3, 3, 1),
...     'points', make_array(1, 2, 2, 10))
>>> table
letter | count | points
a      | 9     | 1
b      | 3     | 2
c      | 3     | 2
z      | 1     | 10
>>> table.append_column('new_col1', make_array(10, 20, 30, 40))
letter | count | points | new_col1
a      | 9     | 1      | 10
b      | 3     | 2      | 20
c      | 3     | 2      | 30
z      | 1     | 10     | 40
>>> table.append_column('new_col2', 'hello')
letter | count | points | new_col1 | new_col2
a      | 9     | 1      | 10       | hello
b      | 3     | 2      | 20       | hello
c      | 3     | 2      | 30       | hello
z      | 1     | 10     | 40       | hello
>>> table.append_column(123, make_array(1, 2, 3, 4))
Traceback (most recent call last):
    ...
ValueError: The column label must be a string, but a int was given
>>> table.append_column('bad_col', [1, 2])
Traceback (most recent call last):
    ...
ValueError: Column length mismatch. New column does not have the same number of rows as table.