__打印时未调用str\uuu方法

import_ get_sql 即使它在 __str__

class Query(object):
    """
    Query builder entry functions
    """
    @classmethod
    def _builder(cls):
        return QueryBuilder()

    @classmethod
    def import_(cls, source_type):
        return cls._builder().import_(source_type)


class QueryBuilder(object):
    """
    Query Builder is the main class that generates sql
    """
    def __init__(self, quote_char='"'):
        self._from = []
        self._import = None
        self._source_type = None
        self.quote_char = quote_char

    def import_(self, source_type):
        if source_type == SourceType.XML:
            raise KeyError('Importing a XML is not supported')
        self._source_type = source_type

    def __str__(self):
        return self.get_sql(quote_char='"')

    def get_sql(self):
        if not (self._import):
            return 'test'
        return 'e'

打印脚本:

importQuery = Query.import_(sourceTypeEnum)
print(importQuery)