007. Python词汇计数

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Popular words

一、问题描述

要求：统计字符串中每个单词的频率，按照出现频率从高到低给出词汇字典。

输入：字符串和需要搜索的词汇列表

输出：词汇字典（键：需要搜索的词汇；值：词频）

注意：

• 比如One, one, ONE等视为同样的单词
• 对于未找到的单词，频率为0

示例：

popular_words('''
When I was One
I had just begun
When I was Two
I was nearly new
''', ['i', 'was', 'three', 'near']) == {
    'i': 4,
    'was': 3,
    'three': 0,
    'near': 0
}

二、解题示例

1. 遍历

def popular_words(text: str, words: list) -> dict:
    # your code here
    text = text.lower().split()
    popular_words = dict(zip(words, [0 for _ in range(len(words))]))

    for item in text:
        if item in words:
            popular_words[item] += 1

    return popular_words


if __name__ == '__main__':
    print("Example:")
    print(popular_words('''
When I was One
I had just begun
When I was Two
I was nearly new
''', ['i', 'was', 'three', 'near']))

    # These "asserts" are used for self-checking and not for an auto-testing
    assert popular_words('''
When I was One
I had just begun
When I was Two
I was nearly new
''', ['i', 'was', 'three', 'near']) == {
        'i': 4,
        'was': 3,
        'three': 0,
        'near': 0
    }
    print("Coding complete!")

2. count函数

def popular_words(text, words):
    lower_count = text.lower().split().count
    return {word: lower_count(word) for word in words}

if __name__ == '__main__':
    print("Example:")
    print(popular_words('''
When I was One
I had just begun
When I was Two
I was nearly new
''', ['i', 'was', 'three', 'near']))

    # These "asserts" are used for self-checking and not for an auto-testing
    assert popular_words('''
When I was One
I had just begun
When I was Two
I was nearly new
''', ['i', 'was', 'three', 'near']) == {
        'i': 4,
        'was': 3,
        'three': 0,
        'near': 0
    }
    print("Coding complete!")

3.

def popular_words(text, words):
    return dict(zip(words, map(text.lower().split().count, words)))

if __name__ == '__main__':
    print("Example:")
    print(popular_words('''
When I was One
I had just begun
When I was Two
I was nearly new
''', ['i', 'was', 'three', 'near']))

    # These "asserts" are used for self-checking and not for an auto-testing
    assert popular_words('''
When I was One
I had just begun
When I was Two
I was nearly new
''', ['i', 'was', 'three', 'near']) == {
        'i': 4,
        'was': 3,
        'three': 0,
        'near': 0
    }
    print("Coding complete!")