Python 字典

字典的示例：

list_0 = {"name": "apple", "count": 5}

1. 添加键 — 值对

alien_0 = {'color': 'green', 'points': 5}
print(alien_0)
alien_0['x_position'] = 0
alien_0['y_position'] = 25
print(alien_0)

输出内容：

添加键 — 值对

2. 修改字典中的值

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

输出内容：

修改字典中的值

3. 删除键 — 值对

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

输出结果：

删除键 — 值对

4. 遍历所有的键 — 值对

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

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

5. 遍历字典中的所有键

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

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

6. 按顺序遍历字典中的所有键

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

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

7. 遍历字典中的所有值，并合并相同的值

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

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

8. 嵌套：字典列表

8.1 示例一：

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)

8.2 示例二：

aliens = []

for alien_number in range(30):
    alien_number = alien_number % 3
    if alien_number == 0:
        new_alien = {'color': 'green', 'points': 5}
    elif alien_number == 1:
        new_alien = {'color': 'yellow', 'points': 10}
    elif alien_number == 2:
        new_alien = {'color': 'red', 'points': 15}
    aliens.append(new_alien)

for alien in aliens[0: 7]:
    print(alien)

print("...")

9. 嵌套：在字典中存储列表

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

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

10. 嵌套：在字典中存储字典

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']
    print("\tFull name: " + full_name.title())
    location = user_info['location']
    print("\tLocation: " + location.title())

本文参考自 《Python 编程：从入门到实践》