django 错误：__init__() 正好采用 1 个参数（给定 2 个）

Question

我编写了一个名为“库”的 sqlalchemy 模型：

class Library(Base):
    __tablename__ = 'library'
    id = Column(Integer, primary_key=True)
    details = Column(String)

    def __init__(self, details):
        self.details = details

    def __repr__(self):
        return u"Library(%s)" % (self.details)  

然后，在 views.py 文件中，我写了：

def is_lib_empty():
    return len(session.query(Library).all()) <= 0

def populateLib():
    new_libs = [Library('one'), Library('two'), Library('three'), Library('four')]
    session.add_all(new_libs)
    session.commit()

def index(request):
    if is_lib_empty():    
        populateLib()

    libs = session.query(Library).all()
    return render_to_response('../templates/index.html',{'libs':libs})  

然后我运行 python manage.py runserver，它显示了一条错误消息：

__init__() takes exactly 1 argument (2 given)

我应该怎么做才能解决这个问题？

TypeError at /
__init__() takes exactly 1 argument (2 given)
Request Method: GET
Django Version: 1.3.1
Exception Type: TypeError
Exception Value:    
__init__() takes exactly 1 argument (2 given)
Exception Location: /cs/wetlab/Limor/workspace/Yeasti/Yeasti/loose_coupling/../loose_coupling/with_sqlalchemy/views.py in populateLib, line 25
Python Executable:  /sw/bin/python2.7
Python Version: 2.7.2
Python Path:    
['/cs/wetlab/Limor/workspace/Yeasti/Yeasti/loose_coupling',
 '/sw/lib/python27.zip',
 '/sw/lib/python2.7',
 '/sw/lib/python2.7/plat-darwin',
 '/sw/lib/python2.7/plat-mac',
 '/sw/lib/python2.7/plat-mac/lib-scriptpackages',
 '/sw/lib/python2.7/lib-tk',
 '/sw/lib/python2.7/lib-old',
 '/sw/lib/python2.7/lib-dynload',
 '/sw/lib/python2.7/site-packages',
 '/sw/lib/python2.7/site-packages/setuptools-0.6c11-py2.7.egg-info']
Server time:    Sun, 1 Jul 2012 05:50:03 -0500  


Environment:
Request Method: GET

Django Version: 1.3.1
Python Version: 2.7.2
Installed Applications:
['loose_coupling.with_sqlalchemy']
Installed Middleware:
('django.middleware.common.CommonMiddleware',)


Traceback:
File "/sw/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  111.                         response = callback(request, *callback_args, **callback_kwargs)
File "/cs/wetlab/Limor/workspace/Yeasti/Yeasti/loose_coupling/../loose_coupling/with_sqlalchemy/views.py" in index
  39.     populateLib()
File "/cs/wetlab/Limor/workspace/Yeasti/Yeasti/loose_coupling/../loose_coupling/with_sqlalchemy/views.py" in populateLib
  25.     new_libs = [Library('one'), Library('two'), Library('three'), Library('four')]

Exception Type: TypeError at /
Exception Value: __init__() takes exactly 1 argument (2 given)

Answer 1

更新：

您始终可以使用默认构造函数，使用关键字参数：

Library(details='some details')

如http://docs.sqlalchemy.org/en/rel_0_7/orm/tutorial.html中所述

这是默认构造函数支持的，不需要覆盖它。无论如何，你的代码应该可以工作，除非某处有一些覆盖......