8 再识Python里的字典

date 2018年12月29日

#前面学习的字典只能存储一个外星人的信息，如果是好多外星人呢？
#或者说一个字典，存储某一类信息，如果要存储好多类信息呢？这时候需要我们用列表来存储字典
#例如下面的程序
alien_0 = {'color': 'green', 'points': 5}
alien_1 = {'color': 'yellow', 'points': 10}
alien_2 = {'color': 'red', 'points': 15}
aliens = [alien_0, alien_1, alien_2] #类似于把所有的字典存储到一个列表中

for alien in aliens:
    print(alien)  
#当然这是很一般的情形，本质上一个字典也可以实现
#下面我们来看更符合实际的一种情况

result

{'color': 'green', 'points': 5}
{'color': 'yellow', 'points': 10}
{'color': 'red', 'points': 15}

#用range()函数生成外星人的代号0-29(注意range()是从0开始的)
aliens = [] #let us creat an empty list first 

for alien_nummber in range(30): 
    new_alien = {'color ': 'green', 'points': 5, 'speed': 'slow'}
    aliens.append(new_alien)  # fill new_alien in aliens *append is '附件' in Chinese
#every aliens has the same characteristic

#try to show the top 5 aliens
for alien in aliens[: 5]:
    print(alien)
print('...')

#show the number of aliens you have created
number = len(aliens)
print("The number of aliens: " + str(number))

result

{'color ': 'green', 'points': 5, 'speed': 'slow'}
{'color ': 'green', 'points': 5, 'speed': 'slow'}
{'color ': 'green', 'points': 5, 'speed': 'slow'}
{'color ': 'green', 'points': 5, 'speed': 'slow'}
{'color ': 'green', 'points': 5, 'speed': 'slow'}
...
The number of aliens: 30

#try to modify the top 3 aliens characteristic
aliens = [] #same example above 
for alien_nummber in range(0,30): 
    new_alien = {'color': 'green', 'speed': 'slow', 'points': 5}
    aliens.append(new_alien) 
#Now let us modify...
for alien in aliens[0 : 3]:
    if alien['color'] is 'green': 
        alien['color'] = 'yellow'
        alien['speed'] = 'medium'
        alien['points'] = 10
#print the top 5 aliens and detect the change
for alien in aliens[0 : 5]:
    print(alien)
print('...')
#Many inexplicable error! such as the 'space','the colon' is different in Chinese and English

result

{'color': 'yellow', 'speed': 'medium', 'points': 10}
{'color': 'yellow', 'speed': 'medium', 'points': 10}
{'color': 'yellow', 'speed': 'medium', 'points': 10}
{'color': 'green', 'speed': 'slow', 'points': 5}
{'color': 'green', 'speed': 'slow', 'points': 5}
...

#On the contrary,how to store lists in a dictionary?
#Let's see the following example
#Information about Pizza 
pizza = {
    'crust': 'thick',  #crust means '壳',topping means '配料'
    'toppings': ['mushrooms', 'extra cheese'] #store a list in a dictionary
    }

print("You ordered a " + pizza['crust'] + "-crust pizza" + "with the following toppings:")

for topping in pizza['toppings']:
    print("\t" + topping)

result

You ordered a thick-crust pizzawith the following toppings:
mushrooms
extra cheese

#Count up students' scores
grade = {
    'Shi shang':['Math - 98', 'Chinese - 96'], #Bear in mind this comma
    'Ding shiyu':['Math - 97','Chinese - 95'], #comma means '逗号'
    'Lv yuetong':['Math - 100','Chinese - 98']
} 
for name, scores in grade.items():
    print("\n" + name.title() + "'s final exam grades are:")
    for score in scores:
        print("\t" + score)

result

Shi Shang's final exam grades are:
Math - 98
Chinese - 96

Ding Shiyu's final exam grades are:
Math - 97
Chinese - 95

Lv Yuetong's final exam grades are:
Math - 100
Chinese - 98

#Use a dictionary in dictionary
#the same example above 
grade = {
    'math' : {'Shishang': 98, 'Lvyuetong': 100, 'Dingshiyu': 97},
    'chinese' : {'Shishang': 96, 'Lvyuetong': 98, 'Dingshiyu': 97}
}  # Notice the form of the definition above
for subjects, scores in grade.items():
    print(subjects)
    print(scores)

result

math
{'Shishang': 98, 'Lvyuetong': 100, 'Dingshiyu': 97}
chinese
{'Shishang': 96, 'Lvyuetong': 98, 'Dingshiyu': 97}

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