60 lines
1.9 KiB
Python
60 lines
1.9 KiB
Python
#!/usr/bin/env python
|
|
|
|
from agate.aggregations.has_nulls import HasNulls
|
|
from agate.computations.base import Computation
|
|
|
|
from agate.data_types import Number
|
|
from agate.exceptions import DataTypeError
|
|
from agate.warns import warn_null_calculation
|
|
|
|
|
|
class PercentChange(Computation):
|
|
"""
|
|
Calculate the percent difference between two columns.
|
|
|
|
:param before_column_name:
|
|
The name of a column containing the "before" :class:`.Number` values.
|
|
:param after_column_name:
|
|
The name of a column containing the "after" :class:`.Number` values.
|
|
"""
|
|
def __init__(self, before_column_name, after_column_name):
|
|
self._before_column_name = before_column_name
|
|
self._after_column_name = after_column_name
|
|
|
|
def get_computed_data_type(self, table):
|
|
return Number()
|
|
|
|
def validate(self, table):
|
|
before_column = table.columns[self._before_column_name]
|
|
after_column = table.columns[self._after_column_name]
|
|
|
|
if not isinstance(before_column.data_type, Number):
|
|
raise DataTypeError('PercentChange before column must contain Number data.')
|
|
|
|
if not isinstance(after_column.data_type, Number):
|
|
raise DataTypeError('PercentChange after column must contain Number data.')
|
|
|
|
if HasNulls(self._before_column_name).run(table):
|
|
warn_null_calculation(self, before_column)
|
|
|
|
if HasNulls(self._after_column_name).run(table):
|
|
warn_null_calculation(self, after_column)
|
|
|
|
def run(self, table):
|
|
"""
|
|
:returns:
|
|
:class:`decimal.Decimal`
|
|
"""
|
|
new_column = []
|
|
|
|
for row in table.rows:
|
|
before = row[self._before_column_name]
|
|
after = row[self._after_column_name]
|
|
|
|
if before is not None and after is not None:
|
|
new_column.append((after - before) / before * 100)
|
|
else:
|
|
new_column.append(None)
|
|
|
|
return new_column
|