43 lines
1.3 KiB
Python
43 lines
1.3 KiB
Python
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#!/usr/bin/env python
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from agate.aggregations.base import Aggregation
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from agate.data_types import Boolean
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class First(Aggregation):
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"""
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Returns the first value that passes a test.
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If the test is omitted, the aggregation will return the first value in the column.
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If no values pass the test, the aggregation will raise an exception.
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:param column_name:
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The name of the column to check.
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:param test:
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A function that takes a value and returns `True` or `False`. Test may be
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omitted when checking :class:`.Boolean` data.
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"""
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def __init__(self, column_name, test=None):
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self._column_name = column_name
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self._test = test
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def get_aggregate_data_type(self, table):
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return table.columns[self._column_name].data_type
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def validate(self, table):
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column = table.columns[self._column_name]
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data = column.values()
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if self._test is not None and len([d for d in data if self._test(d)]) == 0:
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raise ValueError('No values pass the given test.')
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def run(self, table):
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column = table.columns[self._column_name]
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data = column.values()
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if self._test is None:
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return data[0]
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return next((d for d in data if self._test(d)))
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