如何提取后面没有关键字的数字

Question

我想从字符串中获取十进制数字，但后面不跟“/套”。pattern = '(\d{1,}\.{0,1}\d{0,}万{0,1}-{0,1}\d{0,}\.{0,1}\d{0,}万{0,1})元{0,1}(?!/套)'string1 = 'item 1:298元/套起'string2 = 'item 1:298元/m2起'string3 = 'item 1:298/m2起'result1 = re.findall(pattern, string1) #expected [], but return ['1', '298']result2 = re.findall(pattern, string2) #expected [298], but return ['1', '298', '2']result3 = re.findall(pattern, string3) #expected [298], but return ['1', '298', '2']如何得到正确答案？

Answer 1

头脑：

• {0,1} = ?

• {0,}=*

• {1,}=+

使用

(\d+\.?\d*万?-?\d*\.?\d*万?)元?/(?!套)

查看证明

解释

--------------------------------------------------------------------------------

  (                        group and capture to \1:

--------------------------------------------------------------------------------

    \d+                      digits (0-9) (1 or more times (matching

                             the most amount possible))

--------------------------------------------------------------------------------

    \.?                      '.' (optional (matching the most amount

                             possible))

--------------------------------------------------------------------------------

    \d*                      digits (0-9) (0 or more times (matching

                             the most amount possible))

--------------------------------------------------------------------------------

    万                  '万'

--------------------------------------------------------------------------------

    ;?                       ';' (optional (matching the most amount

                             possible))

--------------------------------------------------------------------------------

    -?                       '-' (optional (matching the most amount

                             possible))

--------------------------------------------------------------------------------

    \d*                      digits (0-9) (0 or more times (matching

                             the most amount possible))

--------------------------------------------------------------------------------

    \.?                      '.' (optional (matching the most amount

                             possible))

--------------------------------------------------------------------------------

    \d*                      digits (0-9) (0 or more times (matching

                             the most amount possible))

--------------------------------------------------------------------------------

    万                  '万'

--------------------------------------------------------------------------------

    ;?                       ';' (optional (matching the most amount

                             possible))

--------------------------------------------------------------------------------

  )                        end of \1

--------------------------------------------------------------------------------

  元                  '元'

--------------------------------------------------------------------------------

  ;?                       ';' (optional (matching the most amount

                           possible))

--------------------------------------------------------------------------------

  /                        '/'

--------------------------------------------------------------------------------

  (?!                      look ahead to see if there is not:

--------------------------------------------------------------------------------

    套                 '套'

--------------------------------------------------------------------------------

  )                        end of look-ahead

Answer 2

如果我理解正确的话，使用向前看和向后看这相当简单......

(?<=:)(\d+)(?!.*套)    : Using positive look behind to make sure the number is preceded by a colon, doesn't include the colon in the "full match"

:(\d+)(?!.*套)         : Not using positive look behind; colon is included in "full match" but not in groups

(?<=:)(\d+)(?!.*套)

(?<=                   : Start of positive look behind

    :                  : String to search for

     )                 : End of positive look behind

      (                : Start of capture group

       \d+             : Capture any number 1 or more times

          )            : End of capture group

           (?!         : Start of negative look ahead

              .*       : Greedy "capture anything" before string we're trying to avoid

                套     : String we're trying to avoid

                  )    : End of negative look ahead