正则表达式从字符串中提取时间(例如 7 :30pm, 8 pm, 9.05)

Question

我正在开发一个 Rails 应用程序，它使用外部提要来获取某些事件数据，但令人讨厌的是，它们只提供一个包含时间的字符串。例如:

Doors open at 7:30pm, show starts at 9pm

我的目标是从这些字符串中提取第一次并将其放入日期时间字段。系统需要捕获以下类型的值:

上午 11 点

中午 12 点

下午 1 点

下午 2:15

3.30pm

4.45

5:30

06:15

07:30pm

晚上 8:30

晚上 9.15

但不是这些:

105

2 50

305pm

4 点 15 点

74pm

840am

我认为最好的方法是使用正则表达式并通过一些搜索(特别是 this SO question )我有以下内容:
[0-9]{1,2}(:|.)??[0-9]{0,2}\s?(am|pm|AM|PM)
它部分有效，但不排除任何我不想要的，似乎只捕获 2 和 3 中 am/pm 的第一个字符。

这可以用正则表达式吗？

谢谢!

Answer 1

\b((?:0?[1-9]|1[0-2])(?!\d| (?![ap]))[:.]?(?:(?:[0-5][0-9]))?(?:\s?[ap]m)?)\b

它不支持 24 小时格式，但它强制执行有效时间。向你的正则表达式引擎添加一个不区分大小写的标志，无论它是什么语言，或者用 (i: ) 包裹正则表达式如果支持。

Demo with your sample

正则表达式:

NODE                     EXPLANATION
--------------------------------------------------------------------------------
  \b                       the boundary between a word char (\w) and
                           something that is not a word char
--------------------------------------------------------------------------------
  (                        group and capture to \1:
--------------------------------------------------------------------------------
    (?:                      group, but do not capture:
--------------------------------------------------------------------------------
      0?                       '0' (optional (matching the most
                               amount possible))
--------------------------------------------------------------------------------
      [1-9]                    any character of: '1' to '9'
--------------------------------------------------------------------------------
     |                        OR
--------------------------------------------------------------------------------
      1                        '1'
--------------------------------------------------------------------------------
      [0-2]                    any character of: '0' to '2'
--------------------------------------------------------------------------------
    )                        end of grouping
--------------------------------------------------------------------------------
    (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
      \d                       digits (0-9)
--------------------------------------------------------------------------------
     |                        OR
--------------------------------------------------------------------------------
                               ' '
--------------------------------------------------------------------------------
      (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
        [ap]                     any character of: 'a', 'p'
--------------------------------------------------------------------------------
      )                        end of look-ahead
--------------------------------------------------------------------------------
    )                        end of look-ahead
--------------------------------------------------------------------------------
    [:.]?                    any character of: ':', '.' (optional
                             (matching the most amount possible))
--------------------------------------------------------------------------------
    (?:                      group, but do not capture (optional
                             (matching the most amount possible)):
--------------------------------------------------------------------------------
      (?:                      group, but do not capture:
--------------------------------------------------------------------------------
        [0-5]                    any character of: '0' to '5'
--------------------------------------------------------------------------------
        [0-9]                    any character of: '0' to '9'
--------------------------------------------------------------------------------
      )                        end of grouping
--------------------------------------------------------------------------------
    )?                       end of grouping
--------------------------------------------------------------------------------
    (?:                      group, but do not capture (optional
                             (matching the most amount possible)):
--------------------------------------------------------------------------------
      \s?                      whitespace (\n, \r, \t, \f, and " ")
                               (optional (matching the most amount
                               possible))
--------------------------------------------------------------------------------
      [ap]                     any character of: 'a', 'p'
--------------------------------------------------------------------------------
      m                        'm'
--------------------------------------------------------------------------------
    )?                       end of grouping
--------------------------------------------------------------------------------
  )                        end of \1
--------------------------------------------------------------------------------
  \b                       the boundary between a word char (\w) and
                           something that is not a word char