python学习笔记：第六章 字典

󰃭 2017-04-06

python学习笔记：第六章 字典

一个简单的字典

alien_0 = {'color': 'green', 'points': 5}
print(alien_0['color'])
print(alien_0['points'])

值赋给变量

new_points = alien_0['points']
print ("You just earned " + str(new_points) + " points!")

已有字典中增加键-值

alien_0['x_position'] = 0
alien_0['y_positon'] = 25
print(alien_0)

空字典增加键-值

alien_0 = {}

alien_0['color'] = 'green'
alien_0['points'] = 5
print(alien_0)

修改字典中的键-值

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

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

外星人来了

位置+速度—移动至新位置。

alien_0 = {'x_position': 0, 'y_position': 25, 'speed': 'medium'}
print("Original x_positon: " + 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']))

删除键-值

alien_0 = {'color': 'greem', 'points': 5}
print(alien_0)
del alien_0['points']
print(alien_0)

类似键-值组成的字典

favorite_languages = {
    'jen': 'python',
    'sarah': 'c',
    'edward': 'ruby',
    'phil': 'python',
    }
print(favorite_languages)
print("Sarah's favorite language is " +
      favorite_languages['sarah'].title() +
      ".")

遍历所有键-值

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

for key, value in user_0.items():
    print("\n Key: " + key)
    print("Value: " + value)

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

for name, language in favorite_languages.items():
    print(name.title() + "'s favorite language is " +
          language.title() + ".")

for name in favorite_languages.keys():
    print(name.title())

列表中的元素是不是字典中的键？

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

friends = ['phil', 'sarah']
for name in favorite_languages.keys():
    print(name.title())

    if name in friends:
        print("Hi " + name.title() +
              ", I see your favorite language is " +
              favorite_languages[name].title() + "!")

遍历所有键并排序

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

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

遍历所有值及去掉相同值

for language in favorite_languages.values():
    print(language.title())

for language in set(favorite_languages.values()):
    print(language.title())

字典的列表

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)
print("...")

产生30个外星人，打印前5个

定义一个字典，包含多种参数，然后生成相同字典元素的列表

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

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

print("Total number of aliens: " + str(len(aliens)))

修改某个字典里的键值

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
    elif alien['color'] == 'yellow':
        alien['color'] = 'red'
        alien['speed'] = 'fast'
        alien['points'] =15

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

在字典中存储列表

存储披萨的信息，生成一个字典，字典中的某些keys可能包含多个value（list）

pizza = {
    'crust': 'thick',
    'toppings': ['mushrooms', 'extra cheese'],
    }

描述所点的披萨

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

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

字典中含有列表，怎样读取列表中的元素？

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

print(favorite_languages['edward'][0])

for name, languages in favorite_languages.items():
    if len(languages) == 1:
        print("\n" + name.title() + "'s favorit language is: "  + languages[0].title())
    else:
        print("\n" + name.title() + "'s favorite languages are:")
        for language in languages:
            print("\t" + language.title())

字典中存储字典

uesrs = {
    'aeinstein': {
        'first': 'albert',
        'last': 'einstein',
        'location': 'princeton',
        },

    'mcurie': {
        'first': 'marie',
        'last': 'curie',
        'location': 'paris',
        },
    }

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

    print("\tFull name: " + full_name.title())
    print("\tLocation: " + location.title())