def run(self, table):
"""
:returns:
:class:`decimal.Decimal`
"""
# If the user has provided a total, use that
if self._total is not None:
total = self._total
# Otherwise compute the sum of all the values in that column to
# act as our denominator
else:
total = table.aggregate(Sum(self._column_name))
# Raise error if sum is less than or equal to zero
if total <= 0:
raise DataTypeError(
'The sum of column values must be a positive number')
# Create a list new rows
new_column = []
# Loop through the existing rows
for row in table.rows:
# Pull the value
value = row[self._column_name]
if value is None:
new_column.append(None)
continue
# Try to divide it out of the total
percent = value / total
# And multiply it by 100
percent = percent * 100
# Append the value to the new list
new_column.append(percent)
# Pass out the list
return new_column
def __init__(self, column_name):
self._column_name = column_name
self._sum = Sum(column_name)
