动态添加到类

Question

I've created a new class and I'm trying to add to that class dynamically, I've created a list, that I want to put multiple objects in, then I will iterate over that list in Django (is this the correct way of doing things?)

but I'm getting the below error

TypeError: __init__() takes exactly 9 arguments (1 given)

I know what the error means, I'm just wonder how I go about creating a new instance of my objects and adding to it on the fly easily?

### create User Object
class User:
    def __init__(self, Policy, Level, StartDate, EndDate, StartTime, EndTime, Name, Mobile):
        self.Policy = Policy
        self.Level = Level
        self.StartDate = StartDate
        self.EndDate = EndDate
        self.StartTime = StartTime
        self.EndTime = EndTime
        self.Name = Name
        self.Mobile = Mobile
    def __init__(self):
        pass    


### Get all the Polices ###
lstOnCall = []
for objPolicy in objPolicyData['escalation_policies']:
    strPolicyName = objPolicy['name']   
    if strPolicyName.lower().find('test') == -1:
        for objOnCall in objPolicy['on_call']:
            objUser = User()
            objUser.Policy = strPolicyName
            objUser.Level = objOnCall['level']
            objUser.StartDate = getDate(objOnCall['start'])
            objUser.EndDate = getDate(objOnCall['end'])
            objUser.StartTime = getTime(objOnCall['start'])
            objUser.EndTime = getTime(objOnCall['end'])
            objUser = objOnCall['user']
            objUser.Name = objUser['name']
            objUser.Mobile = getUserMobile(objUser['id'])
            lstOnCall.append(objUser)
print lstOnCall

UPDATE: adding the below works, i just need to know how to print the items now?

def __init__(self):
        pass

the below

for item in lstOnCall:         
    print item()

returns

    print item()
AttributeError: User instance has no __call__ method

Answer 1

You can write a dynamic constructor ( def __init__ ) for your class so:

class User(object):
    __attrs = ['Policy', 'Level', 'StartDate', 'EndDate', 'StartTime',
               'EndTime', 'Name', 'Mobile']

    def __init__(self, **kwargs):
        for attr in self.__attrs:
            setattr(self, attr, kwargs.get(attr, None))

    def __repr__(self):
        return ', '.join(
            ['%s: %r' % (attr, getattr(self, attr)) for attr in self.__attrs])

• The variable __attrs stores the variables names. I used double underscore variable, so that it's inaccessible from extend.

user = User()
print(user.__attrs)
Traceback (most recent call last):
    print(user.__attrs)
AttributeError: 'User' object has no attribute '__attrs'

Yes, there are other method to access double underscore variable, but no one will do that ;)

• The function __repr__ return the string by calling print or str , if the function __str__ doesn't exist.

Now test it

>>> u1 = User(Name='user1')
>>> u2 = User(Name='user2', Policy=1, Level=3)
>>> print(u1)
Policy: None, Level: None, StartDate: None, EndDate: None, StartTime: None, EndTime: None, Name: 'user1', Mobile: None
>>> print(u2)
Policy: 1, Level: 3, StartDate: None, EndDate: None, StartTime: None, EndTime: None, Name: 'user2', Mobile: None

If you use my codes, you can print the items in your case so:

for item in lstOnCall:         
    print item

Other problem of your code
There aren't the definition Function overloading in Python. You can define multiple function with the same name in python. But it doesn't make any sense. Only the last definition remains in your class / module . The previous definitions will be overwritten . What you are doing with

class User:
   def __init__(self, a, b, c):
      ...
   def __init__(self):
      pass

is False . It works in Java or C# but not in Python . The function def __init__(self, a, b, c) will be overwritten. Only the function def __init__(self) exists in your class.

Answer 2

Try this,

class User:
    def __init__(self,*args,**kargs):
         if len(kargs)==0 : ''' No param passed '''
            self.Policy = 'Some'
            self.Level = 0
         else:
            self.Policy = kargs['Policy']
            self.Level = kargs['Level']
            [..]

user= User()
user1= User(Policy='Some',Level=13)

Answer 3

您可以将__init__所有参数默认设置为None ：

def __init__(self, Policy=None, Level=None, etc...):

Answer 4

Convert the positional parameters of your constructor method to named, optional parameters with a useful default value:

class User:
    def __init__(self,  Policy=Null, Level=1, 
                 StartDate="2016-01-01", EndDate="2016-12-31", 
                 StartTime="00:00", EndTime="23:59", 
                 Name="UNKNOWN", Mobile=""):
        self.Policy = Policy
        self.Level = Level
        self.StartDate = StartDate
        self.EndDate = EndDate
        self.StartTime = StartTime
        self.EndTime = EndTime
        self.Name = Name
        self.Mobile = Mobile