64 lines
1.9 KiB
Python
64 lines
1.9 KiB
Python
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#!/usr/bin/env python
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# pylint: disable=W0212
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from collections import OrderedDict
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from agate.data_types import Text
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from agate.tableset import TableSet
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def group_by(self, key, key_name=None, key_type=None):
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"""
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Create a :class:`.TableSet` with a table for each unique key.
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Note that group names will always be coerced to a string, regardless of the
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format of the input column.
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:param key:
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Either the name of a column from the this table to group by, or a
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:class:`function` that takes a row and returns a value to group by.
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:param key_name:
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A name that describes the grouped properties. Defaults to the
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column name that was grouped on or "group" if grouping with a key
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function. See :class:`.TableSet` for more.
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:param key_type:
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An instance of any subclass of :class:`.DataType`. If not provided
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it will default to a :class`.Text`.
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:returns:
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A :class:`.TableSet` mapping where the keys are unique values from
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the :code:`key` and the values are new :class:`.Table` instances
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containing the grouped rows.
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"""
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key_is_row_function = hasattr(key, '__call__')
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if key_is_row_function:
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key_name = key_name or 'group'
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key_type = key_type or Text()
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else:
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column = self._columns[key]
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key_name = key_name or column.name
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key_type = key_type or column.data_type
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groups = OrderedDict()
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for row in self._rows:
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if key_is_row_function:
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group_name = key(row)
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else:
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group_name = row[column.name]
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group_name = key_type.cast(group_name)
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if group_name not in groups:
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groups[group_name] = []
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groups[group_name].append(row)
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output = OrderedDict()
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for group, rows in groups.items():
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output[group] = self._fork(rows)
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return TableSet(output.values(), output.keys(), key_name=key_name, key_type=key_type)
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