如何从字符串列表中检索部分匹配 [英] How to retrieve partial matches from a list of strings

问题描述

有关在 数字 列表中检索部分匹配项的方法，请访问:

For approaches to retrieving partial matches in a numeric list, go to:

• 如何返回匹配条件的列表的子集?

Python:在列表中查找

但是，如果您正在寻找如何检索 字符串 列表的部分匹配项，您会发现以下答案中简明地解释了最佳方法.

But if you're looking for how to retrieve partial matches for a list of strings, you'll find the best approaches concisely explained in the answer below.

SO:具有部分匹配项的Python列表查找显示了如何返回 bool ，如果 list 包含部分匹配的元素(例如 begins ， ends 或包含)一个特定的字符串.但是如何 返回元素本身 ，而不是 True 或 False

SO: Python list lookup with partial match shows how to return a bool, if a list contains an element that partially matches (e.g. begins, ends, or contains) a certain string. But how can you return the element itself, instead of True or False

l = ['ones', 'twos', 'threes']
wanted = 'three'

此处，链接问题中的方法将使用以下方式返回 True :

Here, the approach in the linked question will return True using:

any(s.startswith(wanted) for s in l)

那么如何返回元素'threes'?

推荐答案

• startswith 和 in 中，返回布尔值
• in 运算符是对成员资格的测试.
• 这可以通过 list-comprehension 或 filter
来执行
• 使用带有 in 的 list-comprehension 是最快的测试实现.
• 如果大小写不是问题，请考虑将所有单词映射为小写.
  • l = list(map(str.lower，l)).
  • startswith and in, return a Boolean
  • The in operator is a test of membership.
  • This can be performed with a list-comprehension or filter
  • Using a list-comprehension, with in, is the fastest implementation tested.
  • If case is not an issue, consider mapping all the words to lowercase.
    • l = list(map(str.lower, l)).
    • 使用 filter 创建一个 filter 对象，因此 list()用于显示 list 中的所有匹配值.
    • Using filter creates a filter object, so list() is used to show all the matching values in a list.

    l = ['ones', 'twos', 'threes']
    wanted = 'three'
    
    # using startswith
    result = list(filter(lambda x: x.startswith(wanted), l))
    
    # using in
    result = list(filter(lambda x: wanted in x, l))
    
    print(result)
    [out]:
    ['threes']
    

    列表理解

    l = ['ones', 'twos', 'threes']
    wanted = 'three'
    
    # using startswith
    result = [v for v in l if v.startswith(wanted)]
    
    # using in
    result = [v for v in l if wanted in v]
    
    print(result)
    [out]:
    ['threes']
    

    哪种实施速度更快?

    • 使用 nltk
    中的 words 语料库
    • 带有'three'的单词
      • [三"，三折"，三折"，三折"，三折"，三折"，三折"，三折"，"Theepence"，"theepenny"，"threepennyworth"，"threescore"，"threesome"]

      Which implementation is faster?

      • Using the words corpus from nltk
      • Words with 'three'
        • ['three', 'threefold', 'threefolded', 'threefoldedness', 'threefoldly', 'threefoldness', 'threeling', 'threeness', 'threepence', 'threepenny', 'threepennyworth', 'threescore', 'threesome']

        from nltk.corpus import words
        
        %timeit list(filter(lambda x: x.startswith(wanted), words.words()))
        [out]:
        47.4 ms ± 1.9 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
        
        %timeit list(filter(lambda x: wanted in x, words.words()))
        [out]:
        27 ms ± 1.78 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
        
        %timeit [v for v in words.words() if v.startswith(wanted)]
        [out]:
        34.1 ms ± 768 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
        
        %timeit [v for v in words.words() if wanted in v]
        [out]:
        14.5 ms ± 63.3 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
        

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