在多行字符串中匹配多个模式

Question

我有一些数据，长得像这样：

PMID- 19587274
OWN - NLM
DP  - 2009 Jul 8
TI  - Domain general mechanisms of perceptual decision making in human cortex.
PG  - 8675-87
AB  - To successfully interact with objects in the environment, sensory evidence must
      be continuously acquired, interpreted, and used to guide appropriate motor
      responses. For example, when driving, a red 
AD  - Perception and Cognition Laboratory, Department of Psychology, University of
      California, San Diego, La Jolla, California 92093, USA.

PMID- 19583148
OWN - NLM
DP  - 2009 Jun
TI  - Ursodeoxycholic acid for treatment of cholestasis in patients with hepatic
      amyloidosis.
PG  - 482-6
AB  - BACKGROUND: Amyloidosis represents a group of different diseases characterized by
      extracellular accumulation of pathologic fibrillar proteins in various tissues
AD  - Asklepios Hospital, Department of Medicine, Langen, Germany.
      innere2.longen@asklepios.com

我想写一个正则表达式，能够匹配那些跟PMID、TI和AB相关的句子。

有没有办法用一个正则表达式一次性找到这些句子呢？

我花了差不多一整天在研究正则表达式，结果我找到的最接近的一个是：

reg4 = r'PMID- (?P<pmid>[0-9]*).*TI.*- (?P<title>.*)PG.*AB.*- (?P<abstract>.*)AD'
for i in re.finditer(reg4, data, re.S | re.M): print i.groupdict()

这个表达式只会让我找到第二组数据里的匹配项，而不是所有的。

有没有什么好主意？谢谢！

Answer 1

另一个正则表达式：

reg4 = r'(?<=PMID- )(?P<pmid>.*?)(?=OWN - ).*?(?<=TI  - )(?P<title>.*?)(?=PG  - ).*?(?<=AB  - )(?P<abstract>.*?)(?=AD  - )'

Answer 2

不如不使用正则表达式来完成这个任务，而是用一些简单的代码来处理，比如通过换行符来分割文本，使用.startswith()来检查前缀代码等等。这样写的代码可能会长一些，但大家都能看懂，就不用来StackOverflow寻求帮助了。

Answer 3

怎么样：

import re
reg4 = re.compile(r'^(?:PMID- (?P<pmid>[0-9]+)|TI  - (?P<title>.*?)^PG|AB  - (?P<abstract>.*?)^AD)', re.MULTILINE | re.DOTALL)
for i in reg4.finditer(data):
    print i.groupdict()

输出：

{'pmid': '19587274', 'abstract': None, 'title': None}
{'pmid': None, 'abstract': None, 'title': 'Domain general mechanisms of perceptual decision making in human cortex.\n'}
{'pmid': None, 'abstract': 'To successfully interact with objects in the environment, sensory evidence must\n      be continuously acquired, interpreted, and used to guide appropriate motor\n      responses. For example, when driving, a red \n', 'title': None}
{'pmid': '19583148', 'abstract': None, 'title': None}
{'pmid': None, 'abstract': None, 'title': 'Ursodeoxycholic acid for treatment of cholestasis in patients with hepatic\n      amyloidosis.\n'}
{'pmid': None, 'abstract': 'BACKGROUND: Amyloidosis represents a group of different diseases characterized by\n      extracellular accumulation of pathologic fibrillar proteins in various tissues\n', 'title': None}

编辑

为了让正则表达式更容易理解，我写了一个比较详细的版本（我觉得详细的正则表达式应该用于除了最简单的情况以外的所有情况，但这只是我的看法！）：

#!/usr/bin/python
import re
reg4 = re.compile(r'''
        ^                     # Start of a line (due to re.MULTILINE, this may match at the start of any line)
        (?:                   # Non capturing group with multiple options, first option:
            PMID-\s           # Literal "PMID-" followed by a space
            (?P<pmid>[0-9]+)  # Then a string of one or more digits, group as 'pmid'
        |                     # Next option:
            TI\s{2}-\s        # "TI", two spaces, a hyphen and a space
            (?P<title>.*?)    # The title, a non greedy match that will capture everything up to...
            ^PG               # The characters PG at the start of a line
        |                     # Next option
            AB\s{2}-\s        # "AB  - "
            (?P<abstract>.*?) # The abstract, a non greedy match that will capture everything up to...
            ^AD               # "AD" at the start of a line
        )
        ''', re.MULTILINE | re.DOTALL | re.VERBOSE)
for i in reg4.finditer(data):
    print i.groupdict()

注意，你可以把 ^PG 和 ^AD 替换成 ^\S，这样会更通用（你想要匹配的是每行开头第一个非空格字符之前的所有内容）。

编辑 2

如果你想用一个正则表达式捕获整个内容，可以去掉开头的 (?: 和结尾的 )，并把 | 字符改成 .*?：

#!/usr/bin/python
import re
reg4 = re.compile(r'''
        ^                 # Start of a line (due to re.MULTILINE, this may match at the start of any line)
        PMID-\s           # Literal "PMID-" followed by a space
        (?P<pmid>[0-9]+)  # Then a string of one or more digits, group as 'pmid'
        .*?               # Next part:
        TI\s{2}-\s        # "TI", two spaces, a hyphen and a space
        (?P<title>.*?)    # The title, a non greedy match that will capture everything up to...
        ^PG               # The characters PG at the start of a line
        .*?               # Next option
        AB\s{2}-\s        # "AB  - "
        (?P<abstract>.*?) # The abstract, a non greedy match that will capture everything up to...
        ^AD               # "AD" at the start of a line
        ''', re.MULTILINE | re.DOTALL | re.VERBOSE)
for i in reg4.finditer(data):
    print i.groupdict()

这样就得到了：

{'pmid': '19587274', 'abstract': 'To successfully interact with objects in the environment, sensory evidence must\n      be continuously acquired, interpreted, and used to guide appropriate motor\n      responses. For example, when driving, a red \n', 'title': 'Domain general mechanisms of perceptual decision making in human cortex.\n'}
{'pmid': '19583148', 'abstract': 'BACKGROUND: Amyloidosis represents a group of different diseases characterized by\n      extracellular accumulation of pathologic fibrillar proteins in various tissues\n', 'title': 'Ursodeoxycholic acid for treatment of cholestasis in patients with hepatic\n      amyloidosis.\n'}