python 找不到这个分组名称

Question

我尝试对论文参考文献的格式提出建议。例如学术论文，格式为：

author. dissertation name[D]. place where store it: organization who hold the copy, year in which the dissertation published.

很明显，除年份外，每一项都可能有一些标点符号。例如

Smith. The paper name. The subtitle of paper[D]. United States: MIT, 2011

经常会漏掉place where store it和year，例如

Smith. The paper name. The subtitle of paper[D]. US, 2011
Smith. The paper name. The subtitle of paper[D]. US: MIT

我想这样编程：

import re
reObj = re.compile(
r'.*\[D\]\.  \s*  ((?P<PLACE>[^:]*):){0,1} \s*   (?P<HOLDER>[^:]*)   (?P<YEAR>,\s*(1|2)\d{3}){0,1}',
re.VERBOSE
)

txt = '''Smith. The paper name. The subtitle of paper[D]. US: MIT, 2011
Smith. The paper name. The subtitle of paper[D]. US, 2011
Smith. The paper name. The subtitle of paper[D]. US: MIT'''.split('\n')

for i in txt:
    if reObj.search(i):
        if reObj.search(i).group('PLACE')==None:
            print('missing place')

        if reObj.search(i).group('YEAR')==None:
            print('missing year')
    else:
        print('bad formation')

但我发现没有得到 YEAR 对于我在 txt 中：打印(i) 打印(reObj.search(i).group('HOLDER'))

产出

Smith. The paper name. The subtitle of paper[D]. US: MIT, 2011
MIT, 2011
Smith. The paper name. The subtitle of paper[D]. US, 2011
US, 2011
Smith. The paper name. The subtitle of paper[D]. US: MIT
MIT

for i in txt:
    print(i)
    print(reObj.search(i).group('YEAR'))

产出

Smith. The paper name. The subtitle of paper[D]. US: MIT, 2011
None
Smith. The paper name. The subtitle of paper[D]. US, 2011
None
Smith. The paper name. The subtitle of paper[D]. US: MIT
None

那么，为什么我的命名组失败了，如何解决？谢谢

Answer 1

我觉得你可以使用

reObj = re.compile("""
    \[D\]\.  \s*            # [D]. and 0+ whitespaces
    (?:                     # An  optional alternation group
     (?P<PLACE>[^,:]*)      # Group "PLACE": 0+ chars other than , and :
       (?:                           # An optional sequence of
          : \s* (?P<HOLDER>[^,:]*)   # :, 0+ whitespaces, Group "HOLDER" (0+ non-colons and non-commas)
        )?
        (?:                          # An optional sequence of
          ,\s* (?P<YEAR>[12]\d{3})   # , + 0+ whitespaces, Group "YEAR" (1 or 2 and then three digits
        )?                       
    )?      
    $          # end of string
    """, flags=re.X)

参见 regex and Python demos:

import re
reObj = re.compile(
    r"\[D\]\.\s*(?:(?P<PLACE>[^,:]*)(?::\s*(?P<HOLDER>[^,:]*))?(?:,\s*(?P<YEAR>[12]\d{3}))?)?$",
    re.VERBOSE
)
txt = '''Smith. The paper name. The subtitle of paper[D]. US: MIT, 2011
Smith. The paper name. The subtitle of paper[D]. US, 2011
Smith. The paper name. The subtitle of paper[D]. US: MIT'''.split('\n')

for i in txt:
    print('------------------------\nTESTING {}'.format(i))
    m = reObj.search(i)
    if m:
        if not m.group('PLACE'):
            print('missing place')
        else:
            print(m.group('PLACE'))

    if not m.group('YEAR'):
        print('missing year')
    else:
        print(m.group('YEAR'))

输出：

------------------------
TESTING Smith. The paper name. The subtitle of paper[D]. US: MIT, 2011
US
2011
------------------------
TESTING Smith. The paper name. The subtitle of paper[D]. US, 2011
US
2011
------------------------
TESTING Smith. The paper name. The subtitle of paper[D]. US: MIT
US
missing year

python 找不到这个分组名称

python re can't find this grouped name

python

regex

named