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from agate.aggregations.base import Aggregation
from agate.data_types import Number
from agate.utils import default
class Count(Aggregation):
"""
Count occurences of a value or values.
This aggregation can be used in three ways:
1. If no arguments are specified, then it will count the number of rows in the table.
2. If only :code:`column_name` is specified, then it will count the number of non-null values in that column.
3. If both :code:`column_name` and :code:`value` are specified, then it will count occurrences of a specific value.
:param column_name:
The column containing the values to be counted.
:param value:
Any value to be counted, including :code:`None`.
"""
def __init__(self, column_name=None, value=default):
self._column_name = column_name
self._value = value
def get_aggregate_data_type(self, table):
return Number()
def run(self, table):
if self._column_name is not None:
if self._value is not default:
return table.columns[self._column_name].values().count(self._value)
return len(table.columns[self._column_name].values_without_nulls())
return len(table.rows)
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