SQLAlchemy, AttributeError: 'टपल' वस्तु में कोई विशेषता 'foreign_keys'

Question

मैं निम्नलिखित मॉडल मेरी डेटाबेस स्कीमा का वर्णन करने के लिए है:

team = Team() 

:

from sqlalchemy.ext.declarative import declarative_base 
from sqlalchemy import Column, Integer, String, ForeignKey 
from sqlalchemy.orm import relationship, backref 
import sqlalchemy.dialects.mysql as mysql 

Base = declarative_base() 

class Country(Base): 
    __tablename__ = 'countries' 
    __table_args__ = { 
     'mysql_engine': 'InnoDB', 
     'mysql_charset': 'utf8' 
    } 

    id = Column(mysql.TINYINT(unsigned=True), primary_key=True) 
    name = Column(mysql.VARCHAR(30), nullable=False) 
    competitions = relationship('Competition', backref='country') 


class Competition(Base): 
    __tablename__ = 'competitions' 
    __table_args__ = { 
     'mysql_engine': 'InnoDB', 
     'mysql_charset': 'utf8' 
    } 

    id = Column(mysql.INTEGER(unsigned=True), primary_key=True) 
    name = Column(mysql.VARCHAR(30), nullable=False) 
    country_id = Column(mysql.TINYINT(unsigned=True), ForeignKey('countries.id')) 
    teams = relationship('Team', backref("competition")) 


class Team(Base): 
    __tablename__ = 'teams' 
    __table_args__ = { 
     'mysql_engine': 'InnoDB', 
     'mysql_charset': 'utf8' 
    } 

    id = Column(mysql.INTEGER(unsigned=True), primary_key=True) 
    name = Column(mysql.VARCHAR(30), nullable=False) 
    competition_id = Column(mysql.INTEGER(unsigned=True), ForeignKey('competitions.id'), nullable=False) 

और जब मैं की तरह एक टीम बनाने की कोशिश

Traceback (most recent call last): 
    File "/home/giorgos/apps/Aptana_Studio_3/plugins/org.python.pydev_2.6.0.2012062121/pysrc/pydevd.py", line 1392, in <module> 
    debugger.run(setup['file'], None, None) 
    File "/home/giorgos/apps/Aptana_Studio_3/plugins/org.python.pydev_2.6.0.2012062121/pysrc/pydevd.py", line 1085, in run 
    pydev_imports.execfile(file, globals, locals) #execute the script 
    File "/home/giorgos/Documents/Aptana Studio 3 Workspace/BetPick/tests/insert_models.py", line 21, in <module> 
    team = Team() 
    File "<string>", line 2, in __init__ 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/orm/instrumentation.py", line 309, in _new_state_if_none 
    state = self._state_constructor(instance, self) 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 485, in __get__ 
    obj.__dict__[self.__name__] = result = self.fget(obj) 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/orm/instrumentation.py", line 157, in _state_constructor 
    self.dispatch.first_init(self, self.class_) 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/event.py", line 291, in __call__ 
    fn(*args, **kw) 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py", line 2342, in _event_on_first_init 
    configure_mappers() 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py", line 2258, in configure_mappers 
    mapper._post_configure_properties() 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py", line 1167, in _post_configure_properties 
    prop.init() 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/orm/interfaces.py", line 128, in init 
    self.do_init() 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/orm/properties.py", line 911, in do_init 
    self._determine_joins() 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/orm/properties.py", line 1034, in _determine_joins 
    self.secondary) 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/orm/properties.py", line 1028, in _search_for_join 
    a_subset=mapper.local_table) 
    File "/home/giorgos/.virtualenvs/venv/local/lib/python2.7/site-packages/sqlalchemy/sql/util.py", line 262, in join_condition 
    b.foreign_keys, 
AttributeError: 'tuple' object has no attribute 'foreign_keys' 

मैं गलत क्या कर रहा हूँ:

मैं उपरोक्त आदेश के बाद निम्नलिखित ट्रैसबैक मिल सकता है?

class Competition(Base): 
    # ... 
    teams = relationship('Team', backref="competition") 

documentation on relationship देखें:

Answer 1

backrefCompetition.teams की अपनी घोषणा में एक कीवर्ड के तर्क होना चाहिए। आप स्पष्ट रूप से वापस संदर्भ कॉन्फ़िगर करने के लिए एक backref callable उपयोग कर सकते हैं, लेकिन आप अभी भी backref कीवर्ड का उपयोग करना चाहते हैं: अजगर में त्रुटियों रिपोर्टिंग जब

class Competition(Base): 
    # ... 
    teams = relationship('Team', backref=backref("competition", ... additional keywords ...))