问题取值

Question

我有一个字符串列表

my_strings = [
    "2002-03-04 with Matt",
    "Important: 2016-01-23 with Mary",
    "with Tom on 2015-06-30",
]

我想提取：

日期（始终采用yyyy-mm-dd格式）
人（总是与人在一起）但我不想保持“与”

我能做到：

import re
pattern = r'.*(\d{4}-\d{2}-\d{2}).*with \b([^\b]+)\b.*'
matched = [re.match(pattern, x).groups() for x in my_strings]

但由于模式与"with Tom on 2015-06-30"不匹配而失败。

问题取值

如何指定正则表达式模式与日期或个人在字符串中出现的顺序无关？

和

如何确保groups()方法每次都以相同的顺序返回它们？

我希望输出看起来像这样？

[('2002-03-04', 'Matt'), ('2016-01-23', 'Mary'), ('2015-06-30', 'Tom')]

Answer 1

使用2个单独的正则表达式做什么呢？

my_strings = [
    "2002-03-04 with Matt",
    "Important: 2016-01-23 with Mary",
    "with Tom on 2015-06-30",
]
import re

pattern = r'.*(\d{4}-\d{2}-\d{2})'
dates = [re.match(pattern, x).groups()[0] for x in my_strings]

pattern = r'.*with (\w+).*'
persons = [re.match(pattern, x).groups()[0] for x in my_strings]

output = zip(dates, persons)
print output
## [('2002-03-04', 'Matt'), ('2016-01-23', 'Mary'), ('2015-06-30', 'Tom')]

Answer 2

这应该有效：

my_strings = [
    "2002-03-04 with Matt",
    "Important: 2016-01-23 with Mary",
    "with Tom on 2015-06-30",
]

import re

alternates = r"(?:\b(\d{4}-\d\d-\d\d)\b|with (\w+)|.)*"

for tc in my_strings:
    print(tc)
    m = re.match(alternates, tc)
    if m:
        print("\t", m.group(1))
        print("\t", m.group(2))

输出是：

$ python test.py
2002-03-04 with Matt
     2002-03-04
     Matt
Important: 2016-01-23 with Mary
     2016-01-23
     Mary
with Tom on 2015-06-30
     2015-06-30
     Tom

但是，这样的事情并不完全直观。我鼓励您尽可能使用named groups。

Answer 3

仅出于教育原因，非正则表达式方法可能涉及在“模糊”模式下使用dateutil解析器来提取日期，并使用nltk toolkit named entity recognition来提取名称。完整代码：

import nltk
from nltk import pos_tag, ne_chunk
from nltk.tokenize import SpaceTokenizer
from dateutil.parser import parse


def extract_names(text):
    tokenizer = SpaceTokenizer()
    toks = tokenizer.tokenize(text)
    pos = pos_tag(toks)
    chunked_nes = ne_chunk(pos)

    return [' '.join(map(lambda x: x[0], ne.leaves())) for ne in chunked_nes if isinstance(ne, nltk.tree.Tree)]

my_strings = [
    "2002-03-04 with Matt",
    "Important: 2016-01-23 with Mary",
    "with Tom on 2015-06-30"
]

for s in my_strings:
    print(parse(s, fuzzy=True))
    print(extract_names(s))

打印：

2002-03-04 00:00:00
['Matt']
2016-01-23 00:00:00
['Mary']
2015-06-30 00:00:00
['Tom']

但这可能过于复杂了。

Answer 4

如果您使用Python的新 正则表达式 模块，则可以使用conditionals获取保证匹配2件物品。

我认为这更像是执行无序匹配的标准。

(?:.*?(?:(?(1)(?!))\b(\d{4}-\d\d-\d\d)\b|(?(2)(?!))with[ ](\w+))){2}

扩展

 (?:
      .*? 
      (?:
           (?(1)(?!))
           \b 
           ( \d{4} - \d\d - \d\d )       # (1)
           \b 
        |  (?(2)(?!))
           with [ ] 
           ( \w+ )                       # (2)
      )
 ){2}

正则表达式以一致的顺序提取字符串的不同部分

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4 个答案: