python - 用于提取日期中月份和年份组合的正则表达式

Question

我正在使用正则表达式提取文本中日期对的月份和年份:

regex = (
    r"((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?(t)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)"
    r"\s?[\.\s\’\’\,\/\'\,\‘\-\–\—]?\s?(\d{4}|\d{2})?\s?\s?((to)|[\|\-\–\—])\s?\s?"
    r"((Jan(uary)?|Feb(ruary)?|Mar(ch)?|Apr(il)?|May|Jun(e)?|Jul(y)?|Aug(ust)?|Sep(tember)?(t)?|Oct(ober)?|Nov(ember)?|Dec(ember)?)"
    r"\s?[\.\s\’\’\,\/\'\,\‘\-\–\—]?\s?(\d{4}|\d{2})|(Present|Now|till\s?(now|date|today)?|current)))"
)

当我使用一些包含月份日期的输入测试正则表达式时，在某些输入中包含月份中的某天，而在其他输入中不包含:

lst = [
    'July 2014 - 28th August 2014',
    'Jan 2012 - 3rd sep 2014',
    'Jan 2008 - May 2012',
    'Jan 2008 and May 2012'
]
for i in lst:
    word = re.finditer(regex,i,re.IGNORECASE)
    for match in word:
        print(match.group())

我得到以下输出:

Jan 2008 - May 2012

但我的预期输出是:

July 2014 - August 2014
Jan 2012 - sep 2014
Jan 2008 - May 2012

我需要更改什么才能使正则表达式与日期中的可选日期相匹配？当日期字符串包含日期时，它始终是带有 st、nd、rd 或 th 的序数> 后缀。

Answer 1

您不能在单个匹配操作期间“跳过”字符串的一部分，因此如果您有 26th August，则您不能只匹配或捕获 26 August。在这些情况下，您要么需要捕获匹配的部分然后将它们连接起来，要么替换您不需要的部分作为后处理步骤。

所以，在这里，我将使用后处理替换方法

import re


day = r'(?:((?:0?[1-9]|[12]\d|3[01])(?:\s*(?:st|[rn]d|th))?)\s*)?'
month = r'(Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|June?|July?|Aug(?:ust)?|Sep(?:t(?:ember)?)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?)' 
year = r'(\d{2}(?:\d{2})?)'
rx_valid = re.compile( fr'\b{day}{month}\s*{year}\s*[-—–]\s*{day}{month}\s*{year}(?!\d)', re.IGNORECASE )
rx_ordinal = re.compile( r'\s*\d+\s*(?:st|[rn]d|th)', re.IGNORECASE )

lst = [
    'July 2014 - 28th August 2014',
    'Jan 2012 - 3rd sep 2014',
    'Jan 2008 - May 2012',
    'Jan 2008 and May 2012'
]
for i in lst:
    word = rx_valid.finditer(i)
    for match in word:
        print(rx_ordinal.sub("", match.group()))

输出:

July 2014 - August 2014
Jan 2012 - sep 2014
Jan 2008 - May 2012

参见 Python demo和 regex demo .