1. 遍历字典中的键－值对：

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    user_0 = {
        'username': 'efermi',
        'first': 'enrico',
        'last': 'fermi',
    }
     
    for key, value in user_0.items():
        print("\nKey: " + key)
        print("Value: " + value)
     
    # 结果为：
    #
    # Key: first
    # Value: enrico
    #
    # Key: last
    # Value: fermi
    #
    # Key: username
    # Value: efermi

    键－值对的返回顺序不一定与存储顺序相同。

  1. 遍历字典中的键：

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    favorite_languages = {
        'jen': 'python',
        'sarah': 'c',
        'edward': 'ruby',
        'phil': 'python',
    }
     
    for name in favorite_languages.keys():
        print(name.title())
     
    print("\n默认遍历键：")
    for name in favorite_languages:
        print(name.title())
     
    # Jen
    # Edward
    # Sarah
    # Phil
    #
    # 默认遍历键：
    # Jen
    # Edward
    # Sarah
    # Phil

  2. 使用 values() 方法遍历字典中的所有值：

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    favorite_languages = {
        'jen': 'python',
        'sarah': 'c',
        'edward': 'ruby',
        'phil': 'python',
    }
     
    print("The following languages have been metioned:")
    for language in favorite_languages.values():
        print(language.title())
     
    # The following languages have been metioned:
    # Python
    # Ruby
    # Python
    # C

    使用集合（set()）去除重复项：

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    favorite_languages = {
        'jen': 'python',
        'sarah': 'c',
        'edward': 'ruby',
        'phil': 'python',
    }
     
    print("The following languages have been metioned:")
    for language in set(favorite_languages.values()):
        print(language.title())
     
    # The following languages have been metioned:
    # Python
    # C
    # Ruby

    ​