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import datetime
from agate.aggregations.base import Aggregation
from agate.data_types import Number, TimeDelta
from agate.exceptions import DataTypeError
class Sum(Aggregation):
"""
Calculate the sum of a column.
:param column_name:
The name of a column containing :class:`.Number` data.
"""
def __init__(self, column_name):
self._column_name = column_name
def get_aggregate_data_type(self, table):
column = table.columns[self._column_name]
if isinstance(column.data_type, (Number, TimeDelta)):
return column.data_type
def validate(self, table):
column = table.columns[self._column_name]
if not isinstance(column.data_type, (Number, TimeDelta)):
raise DataTypeError('Sum can only be applied to columns containing Number or TimeDelta data.')
def run(self, table):
column = table.columns[self._column_name]
start = 0
if isinstance(column.data_type, TimeDelta):
start = datetime.timedelta()
return sum(column.values_without_nulls(), start)
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