Python类-每个类都调用新ID

Question

is it possible to store a class instance as a new instance. For example,

class ClassName(object):
    def __init__(self, **kw):
         self._name = ''
         self._time = float(timeString)


         for attr, val in kw.items():
               if val == None:
                  continue
               setattr(self, '_' + attr, val)

    def getName(self): return self._name
    name = property(getName)

but lets say we store the instance in a list like so..

cl = ClassName('name1')
cl2 = ClassName('name2')
li = list()
li.append(cl)
li.append(cl2)

and then we iterate through them..

for c in li:
    print( c.name )

would they have different values, or will it be the same, if so how can I give the class instances a unique id?

Answer 1

If I understand what you mean, then yes: they will have different values. Fixing the problems mentioned in the comments:

class ClassName(object):
    def __init__(self, **kw):
         self._name = ''
         for attr, val in kw.items():
               if val == None:
                  continue
               setattr(self, '_' + attr, val)

    def getName(self): return self._name
    name = property(getName)

cl = ClassName(name='name1')
cl2 = ClassName(name='name2')
li = list()
li.append(cl)
li.append(cl2)

Then:

>>> li[0].name
'name1'
>>> li[1].name
'name2'

(the names you set with your keyword arguments).

Answer 2

Using the dictionary object that tracks a class's variables, it is possible to add and remove variables of a class.

Simply pass a dictionary to the update() method of the objects built-in dictionary, __dict__ . The key will be the variable name that is accessible from the class.

class EmptyClass: 
    pass

var_name = 'new_variable'
var_value = 'This variable is a test, anything can go here'

obj = EmptyClass()
obj.__dict__.update( {var_name: var_value} )

print obj.new_variable

See the add_food() function below for a real example.

Example

class Food:
    def __init__( self, name, description ):
        self.name = name
        self.description = description
    def __str__(self): return '<Food: name=%s, description=%s' % (self.name, self.description)


class Foods:
    def __init__( self, category, *foods ):
        self.category = category
        self.foods = {}

        if foods:
            self.add_foods( *foods )

    def add_food( self, food, update=True ):
        self.foods[food.name] = food
        if update:
            self.__dict__.update( {food.name.replace(' ', '_'): food} )

    def add_foods( self, *foods ):
        for food in foods:
            # Set update to false, so an update doesn't happen
            # more than once
            self.add_food( food, False )

        new_food = { food.name: food for food in foods }
        self.__dict__.update( new_food )

apple = Food('apple', 'Round and red')
grape = Food('grape', 'small, round and purple') 

# Our add_food() method handles removing the space and putting
# an underscore. Variables can't have spaces in them!
apple2 = Food('green apple', 'Round and green') 

fruits = Foods('fruits', apple, grape)
print fruits.apple
print fruits.grape

fruits.add_food( apple2 )
print fruits.green_apple


print
print fruits.foods['apple']
print fruits.foods['grape']
print fruits.foods['green apple']