98 lines
3.2 KiB
Python
98 lines
3.2 KiB
Python
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#!/usr/bin/env python
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# pylint: disable=W0212
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from agate.type_tester import TypeTester
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from agate.rows import Row
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from agate import utils
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def normalize(self, key, properties, property_column='property', value_column='value', column_types=None):
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"""
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Create a new table with columns converted into rows values.
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For example:
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+---------+----------+--------+-------+
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| name | gender | race | age |
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+=========+==========+========+=======+
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| Jane | female | black | 24 |
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+---------+----------+--------+-------+
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| Jack | male | white | 35 |
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+---------+----------+--------+-------+
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| Joe | male | black | 28 |
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+---------+----------+--------+-------+
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can be normalized on columns 'gender', 'race' and 'age':
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+---------+-----------+---------+
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| name | property | value |
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+=========+===========+=========+
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| Jane | gender | female |
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+---------+-----------+---------+
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| Jane | race | black |
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+---------+-----------+---------+
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| Jane | age | 24 |
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+---------+-----------+---------+
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| ... | ... | ... |
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+---------+-----------+---------+
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This is the opposite of :meth:`.Table.denormalize`.
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:param key:
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A column name or a sequence of column names that should be
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maintained as they are in the normalized self. Typically these
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are the tables unique identifiers and any metadata about them.
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:param properties:
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A column name or a sequence of column names that should be
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converted to properties in the new self.
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:param property_column:
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The name to use for the column containing the property names.
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:param value_column:
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The name to use for the column containing the property values.
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:param column_types:
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A sequence of two column types for the property and value column in
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that order or an instance of :class:`.TypeTester`. Defaults to a
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generic :class:`.TypeTester`.
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:returns:
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A new :class:`.Table`.
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"""
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from agate.table import Table
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new_rows = []
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if not utils.issequence(key):
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key = [key]
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if not utils.issequence(properties):
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properties = [properties]
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new_column_names = key + [property_column, value_column]
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row_names = []
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for row in self._rows:
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k = tuple(row[n] for n in key)
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left_row = list(k)
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if len(k) == 1:
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row_names.append(k[0])
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else:
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row_names.append(k)
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for f in properties:
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new_rows.append(Row((left_row + [f, row[f]]), new_column_names))
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key_column_types = [self._column_types[self._column_names.index(name)] for name in key]
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if column_types is None or isinstance(column_types, TypeTester):
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tester = TypeTester() if column_types is None else column_types
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force_update = dict(zip(key, key_column_types))
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force_update.update(tester._force)
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tester._force = force_update
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new_column_types = tester.run(new_rows, new_column_names)
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else:
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new_column_types = key_column_types + list(column_types)
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return Table(new_rows, new_column_names, new_column_types, row_names=row_names)
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