如何添加兩個python字典，使不等於成爲零？

Question

我需要一點幫助。我是一個新的Python編碼器。我需要很多幫助。所以，我想在兩個字典中添加不同的變量。一個例子是：

x = {'a':1, 'b':2} 

y = {'b':1, 'c':2} 

我要替換這些值，使得它看起來像：

x = {'a':1, 'b':2, 'c':0} 

y = {'a':0, 'b':1, 'c':2} 

Answer 1

>>> x = {'a':1, 'b':2} 
>>> y = {'b':1, 'c':2} 
>>> for k in y: 
... x.setdefault(k, 0) 
... 
0 
2 
>>> for k in x: 
... y.setdefault(k, 0) 
... 
0 
2 
1 
>>> x 
{'a': 1, 'c': 0, 'b': 2} 
>>> y 
{'a': 0, 'c': 2, 'b': 1} 

Answer 2

>>> x = {'a':1, 'b':2} 
>>> y = {'b':1, 'c':2} 
>>> keys = x.viewkeys() | y.viewkeys() #returns union of keys in x and y 
>>> x = {k : x.get(k,0) for k in keys} 
>>> y = {k : y.get(k,0) for k in keys} 
>>> x 
{'a': 1, 'c': 0, 'b': 2} 
>>> y 
{'a': 0, 'c': 2, 'b': 1} 

變化的字典就地：

>>> x = {'a':1, 'b':2} 
>>> y = {'b':1, 'c':2} 
>>> diff_x = y.viewkeys() - x.viewkeys() 
>>> diff_y = x.viewkeys() - y.viewkeys() 
#if you're using a mutable object as value instead of 0, 
#then you've to use a dict comprehension instead of dict.fromkeys. 
>>> x.update(dict.fromkeys(diff_x,0)) 
>>> y.update(dict.fromkeys(diff_y,0)) 
>>> x 
{'a': 1, 'c': 0, 'b': 2} 
>>> y 
{'a': 0, 'c': 2, 'b': 1} 

Answer 3

如果你需要一個新的字典作爲結果，這個解決方案會很好：

>>> x = {'a':1, 'b':2} 
>>> y = {'b':1, 'c':2} 
>>> dict(dict.fromkeys(y, 0), **x) 
{'a': 1, 'c': 0, 'b': 2} 
>>> dict(dict.fromkeys(x, 0), **y) 
{'a': 0, 'c': 2, 'b': 1}