增加价值的现有字典的键

Question

cars = {'2012':'BMW', '2013':'Ford'} 
new_cars = ['Fiat', 'Renault'] 

我试图让：

cars = {'2012':['BMW', 'Fiat'], '2013':['Ford', 'Renault']} 

在0位置从new_cars意味着元素被添加到cars'项目在0位置等。

我申请一个解决方案，我发现的地方，但它的缺陷：

for car in new_cars: 
    for k,v in cars.iteritems(): 
     cars[k] = [cars[k], car] 

赞赏任何帮助。

Answer 1

你必须让你的价值成为一个清单。

例如：

>>> cars = {} 
>>> cars['2012'] = ['BMW', ' Fiat'] 
>>> cars['2013'] = ['Ford', 'Renault'] 
>>> cars 
{'2013': ['Ford', 'Renault'], '2012': ['BMW', ' Fiat']} 
>>> cars['2012'].append('Toyota') 
>>> cars 
{'2013': ['Ford', 'Renault'], '2012': ['BMW', ' Fiat', 'Toyota']} 
>>> cars['2012'] 
['BMW', ' Fiat', 'Toyota'] 

更健壮的例子：

from collections import defaultdict 

# initiate the dict 
cars = defaultdict(list) 

# function for adding cars 
def add_cars(year, new_cars): 
    if isinstance(cars, (list, set)): 
     # if more than 1 new_cars 
     cars[year].extend(new_cars) 
    else: 
     cars[year].append(new_cars) 

# add starting cars 
add_cars('2012', 'BMW') 
add_cars('2013', 'Ford') 
# add new cars 
add_cars('2012', 'Fiat') 
add_cars('2013', 'Renault') 
# view 
print cars 

>>> 
defaultdict(<type 'list'>, {'2013': ['Ford', 'Renault'], '2012': ['BMW', 'Fiat']}) 

还拥有一本字典来做到这一点的选项：

>>> cars = {'2012':['BMW'], '2013':['Ford']} 
>>> new_cars = {'2012':['Fiat'], '2013':['Renault']} 
>>> for k, v in new_cars.iteritems(): 
    cars[k].extend(v) 


>>> cars 
{'2013': ['Ford', 'Renault'], '2012': ['BMW', 'Fiat']}