如何将元组列表中的两个元素分组为字典？

Question

我想总结水果和颜色。有水果的元组及其相应颜色的名单，我希望计算的黄色的水果，然后构造一个词典：

yellowfruit= { 'banana': 1, 'grape' : 2, 'orange': 2, 'peach': '4', 'pear':1 } 

以下是水果的信息

fruit= [ 
       ('apple', 'green'), 
       ('apple', 'red'), 
       ('banana', 'yellow'), 
       ('grape', 'green'), 
       ('grape', 'yellow'), 
       ('grape', 'yellow'), 
       ('grape', 'red'), 
       ('orange', 'yellow'), 
       ('orange', 'yellow'), 
       ('mango', 'green'), 
       ('peach', 'yellow'), 
       ('peach', 'red'), 
       ('peach', 'yellow'), 
       ('peach', 'yellow'), 
       ('peach', 'red'), 
       ('peach', 'yellow'), 
       ('peach', 'red'), 
       ('pear', 'yellow'), 
      ] 

这些是我的意见代码：

fruit= [ 
     ('apple', 'green'), 
     ('apple', 'red'), 
     ('banana', 'yellow'), 
     ('grape', 'green'), 
     ('grape', 'yellow'), 
     ('grape', 'yellow'), 
     ('grape', 'red'), 
     ('orange', 'yellow'), 
     ('orange', 'yellow'), 
     ('mango', 'green'), 
     ('peach', 'yellow'), 
     ('peach', 'red'), 
     ('peach', 'yellow'), 
     ('peach', 'yellow'), 
     ('peach', 'red'), 
     ('peach', 'yellow'), 
     ('peach', 'red'), 
     ('pear', 'yellow'), 
    ] 

yellowfruit = { } # create an empty dictionary 
fruitname = fruit[0][0] # 'apple' is the first fruit 
for i in range(len(fruit)): # loop over the tuples in the fruit list 

    if fruit[i][0] == fruitname: 
     if fruit[i][1] == 'yellow': 
     # for the same kind of fruit, if its colour is yellow, count update for 1 
      n += 1 
     else: # if the same kind of fruit but not the colour of yellow 
      continue 

    else: 
     n = 1 # if not the same kind of fruit, refill the count as 1 
     fruitname = fruit[i][0] # if the fruit change, always update the current item as the fruit name 
    yellowfruit[fruitname] = n # create the dictionary 

print(yellowfruit) 

结果：

{'peach': 4, 'banana': 1, 'orange': 2, 'grape': 3, 'pear': 1, 'mango': 1} 

问题是什么？

Answer 1

你依靠的是按水果排序的元组，但事实并非总是如此。为了处理水果在词典yellow_fruit中存在或不存在的两种情况，我们使用yellow_fruit.get(fruit, 0)，其或者返回yellow_fruit[fruit]（如果fruit存在于yellow_fruit中）或0（如果它不存在）。请注意，字典是无序的，所以如果您重新运行程序，打印的键/值对可以自行排列。

tuple_list = [ 
    ('apple', 'green'), 
    ('apple', 'red'), 
    ('banana', 'yellow'), 
    ('grape', 'green'), 
    ('grape', 'yellow'), 
    ('grape', 'yellow'), 
    ('grape', 'red'), 
    ('orange', 'yellow'), 
    ('orange', 'yellow'), 
    ('mango', 'green'), 
    ('peach', 'yellow'), 
    ('peach', 'red'), 
    ('peach', 'yellow'), 
    ('peach', 'yellow'), 
    ('peach', 'red'), 
    ('peach', 'yellow'), 
    ('peach', 'red'), 
    ('pear', 'yellow'), 
] 

yellow_fruit = {} 
for fruit, colour in tuple_list: 
    if colour == 'yellow': 
     yellow_fruit[fruit] = yellow_fruit.get(fruit, 0) + 1 
print(yellow_fruit) # {'banana': 1, 'orange': 2, 'grape': 2, 'peach': 4, 'pear': 1}