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(in index.rst) to a separate performance page, the header needs to be changed
from === to ***, the filename extension needs to be changed from .inc.rst to
.rst, and a link needs to be added in the subpackage toctree
.. _astropy-table-performance:
Performance Tips
================
Constructing |Table| objects row-by-row using
:meth:`~astropy.table.Table.add_row` can be very slow::
>>> from astropy.table import Table
>>> t = Table(names=['a', 'b'])
>>> for i in range(100):
... t.add_row((1, 2))
If you do need to loop in your code to create the rows, a much faster approach
is to construct a list of rows and then create the Table object at the very
end::
>>> rows = []
>>> for i in range(100):
... rows.append((1, 2))
>>> t = Table(rows=rows, names=['a', 'b'])
Writing a |Table| with |MaskedColumn| to ``.ecsv`` using
:meth:`~astropy.table.Table.write` can be very slow::
>>> from astropy.table import Table
>>> import numpy as np
>>> x = np.arange(10000, dtype=float)
>>> tm = Table([x], masked=True)
>>> tm.write('tm.ecsv', overwrite=True) # doctest: +SKIP
If you want to write ``.ecsv`` using :meth:`~astropy.table.Table.write`,
then use ``serialize_method='data_mask'``.
It uses the non-masked version of data and it is faster::
>>> tm.write('tm.ecsv', overwrite=True, serialize_method='data_mask') # doctest: +SKIP
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