python入门-字典

1 python是使用{}来表示字典

字典是一系列的键值对

alien_0={'color':'green','point':5}

 

2 访问字典中的值

new_point = alien_0['point']
print("you just earned "+str(new_point)+" points!")

3  添加，修改，空，删除 字典

alien_0 = {}
alien_0['color'] = 'green'
alien_0['point'] =5

print(alien_0)

alien_0 = {'color':'green'}
print("The alien is "+alien_0['color']+".")

alien_0['color'] = 'yellow'
print("The alien is " + alien_0['color'] + ".")

alien_0 = {'x_position':0,'y_position':25,'speed':'medium'}
print("Original x-position:" + str(alien_0['x_position']))

if alien_0['speed'] == 'slow':
    x_increment = 1
elif alien_0['speed'] == 'medium':
    x_increment = 2
else :
    x_increment = 3

alien_0['x_position'] = alien_0['x_position'] + x_increment
print('New x-position:' + str(alien_0['x_position']))

alien_0 = {'color':'green','point':5}
print(alien_0)

del alien_0['point']
print(alien_0)

多行输入

favorite_lanage = {
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
    }

print("sarah's favorite language is " +
      favorite_lanage['sarah'].title()+
      ".")

 

4 遍历字典

user_0 = {
    'username':'efermi',
    'first':'enrico',
    'last':'erimi',
}

for key,value in user_0.items():
    print('\nkey:' + key)
    print('Value:' + value)

key和value可以自定义

 

5遍历字典中的所有键

favorite_lanage = {
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
    }
for name in favorite_lanage.keys():
    print(name.title())

 

6按照顺序遍历字典中的所有键

favorite_lanage = {
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
    }

for name in sorted(favorite_lanage.keys()):
    print(name.title() + ", thank you for taking the poll.")

 

7 遍历字典中的值

favorite_lanage = {
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
    }

for name in favorite_lanage.values():
    print(name.title() + ", have been mentioned.")

8 去重用 set()

favorite_lanage = {
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
    }


for name in set(favorite_lanage.values()):
    print(name.title() + ", have been mentioned.")

9 嵌套

把字典存储在列表中，或者把列表作为值存储在字典中，这叫做嵌套

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]

for alien in aliens:
    print(alien)

aliens = []

for alien_number in range(30):
    new_alien = {'color':'green','points':5,'speed':'slow'}
    aliens.append(new_alien)

for alien in aliens[:3]:
    if alien['color']=='green':
        alien['color']='yellow'
        alien['speed']='medium'
        alien['points']=10

for alien in aliens[0:5]:
    print(alien)
print('...')

 

10 字典中存储列表

 

favorite_languages = {
    'jen':['python','ruby'],
    'sarah':['c'],
    'edward':['ruby','go'],
    'phil':['python','haskell']
}

for name,languages in favorite_languages.items():
    print("\n" + name.title() + "'s favorite languages are:" )
    for language in languages:
        print("\t" + language.title())

11 字典中存储字典

users = {
    'aeinstein': {
        'first':'albert',
        'last':'einstein',
        'location':'princeton',
    },
    'mcurie':{
        'first':'marie',
        'last':'curie',
        'location':'paris',
    }
}

for username,user_info in users.items():
    print("\nusername: " +username)
    full_name = user_info['first']+" "+user_info['last']
    location = user_info['location']

    print("\tfull name:"+full_name.title())
    print("\tlocation:"+location.title())