我们从Python开源项目中,提取了以下17个代码示例,用于说明如何使用django.db.models.aggregates.StdDev()。
def check_expression_support(self, expression): bad_fields = (fields.DateField, fields.DateTimeField, fields.TimeField) bad_aggregates = (aggregates.Sum, aggregates.Avg, aggregates.Variance, aggregates.StdDev) if isinstance(expression, bad_aggregates): for expr in expression.get_source_expressions(): try: output_field = expr.output_field if isinstance(output_field, bad_fields): raise NotImplementedError( 'You cannot use Sum, Avg, StdDev, and Variance ' 'aggregations on date/time fields in sqlite3 ' 'since date/time is saved as text.' ) except FieldError: # Not every subexpression has an output_field which is fine # to ignore. pass
def supports_stddev(self): """Confirm support for STDDEV and related stats functions.""" try: self.connection.ops.check_expression_support(StdDev(1)) return True except NotImplementedError: return False
def check_expression_support(self, expression): bad_fields = (fields.DateField, fields.DateTimeField, fields.TimeField) bad_aggregates = (aggregates.Sum, aggregates.Avg, aggregates.Variance, aggregates.StdDev) if isinstance(expression, bad_aggregates): try: output_field = expression.input_field.output_field if isinstance(output_field, bad_fields): raise NotImplementedError( 'You cannot use Sum, Avg, StdDev and Variance aggregations ' 'on date/time fields in sqlite3 ' 'since date/time is saved as text.') except FieldError: # not every sub-expression has an output_field which is fine to # ignore pass