46 lines
1.2 KiB
Python
46 lines
1.2 KiB
Python
|
#!/usr/bin/env python
|
||
|
|
|
||
|
|
from decimal import Decimal
|
||
|
|
|
||
|
|
from agate.aggregations.base import Aggregation
|
||
|
|
from agate.data_types import Number, Text
|
||
|
|
from agate.exceptions import DataTypeError
|
||
|
|
|
||
|
|
|
||
|
|
class MaxLength(Aggregation):
|
||
|
|
"""
|
||
|
|
Find the length of the longest string in a column.
|
||
|
|
|
||
|
|
Note: On Python 2.7 this function may miscalcuate the length of unicode
|
||
|
|
strings that contain "wide characters". For details see this StackOverflow
|
||
|
|
answer: http://stackoverflow.com/a/35462951
|
||
|
|
|
||
|
|
:param column_name:
|
||
|
|
The name of a column containing :class:`.Text` data.
|
||
|
|
"""
|
||
|
|
def __init__(self, column_name):
|
||
|
|
self._column_name = column_name
|
||
|
|
|
||
|
|
def get_aggregate_data_type(self, table):
|
||
|
|
return Number()
|
||
|
|
|
||
|
|
def validate(self, table):
|
||
|
|
column = table.columns[self._column_name]
|
||
|
|
|
||
|
|
if not isinstance(column.data_type, Text):
|
||
|
|
raise DataTypeError('MaxLength can only be applied to columns containing Text data.')
|
||
|
|
|
||
|
|
def run(self, table):
|
||
|
|
"""
|
||
|
|
:returns:
|
||
|
|
:class:`int`.
|
||
|
|
"""
|
||
|
|
column = table.columns[self._column_name]
|
||
|
|
|
||
|
|
lens = [len(d) for d in column.values_without_nulls()]
|
||
|
|
|
||
|
|
if not lens:
|
||
|
|
return Decimal('0')
|
||
|
|
|
||
|
|
return Decimal(max(lens))
|