在 Python 中匹配组 [英] Match groups in Python

问题描述

Python 中是否有一种方法可以在不显式创建匹配对象的情况下访问匹配组(或其他美化以下示例的方法)?

Is there a way in Python to access match groups without explicitly creating a match object (or another way to beautify the example below)?

这里有一个例子来阐明我提出这个问题的动机:

Here is an example to clarify my motivation for the question:

遵循 Perl 代码

if    ($statement =~ /I love (\w+)/) {
  print "He loves $1\n";
}
elsif ($statement =~ /Ich liebe (\w+)/) {
  print "Er liebt $1\n";
}
elsif ($statement =~ /Je t\'aime (\w+)/) {
  print "Il aime $1\n";
}

翻译成Python

m = re.search("I love (\w+)", statement)
if m:
  print "He loves",m.group(1)
else:
  m = re.search("Ich liebe (\w+)", statement)
  if m:
    print "Er liebt",m.group(1)
  else:
    m = re.search("Je t'aime (\w+)", statement)
    if m:
      print "Il aime",m.group(1)

看起来很别扭(if-else-cascade，匹配对象创建).

looks very awkward (if-else-cascade, match object creation).

推荐答案

您可以创建一个小类，返回调用 match 的布尔结果，并 保留匹配的组以供后续检索:>

You could create a little class that returns the boolean result of calling match, and retains the matched groups for subsequent retrieval:

import re

class REMatcher(object):
    def __init__(self, matchstring):
        self.matchstring = matchstring

    def match(self,regexp):
        self.rematch = re.match(regexp, self.matchstring)
        return bool(self.rematch)

    def group(self,i):
        return self.rematch.group(i)


for statement in ("I love Mary", 
                  "Ich liebe Margot", 
                  "Je t'aime Marie", 
                  "Te amo Maria"):

    m = REMatcher(statement)

    if m.match(r"I love (\w+)"): 
        print "He loves",m.group(1) 

    elif m.match(r"Ich liebe (\w+)"):
        print "Er liebt",m.group(1) 

    elif m.match(r"Je t'aime (\w+)"):
        print "Il aime",m.group(1) 

    else: 
        print "???"

更新 Python 3 打印为函数和 Python 3.8 赋值表达式 - 现在不需要 REMatcher 类:

Update for Python 3 print as a function, and Python 3.8 assignment expressions - no need for a REMatcher class now:

import re

for statement in ("I love Mary",
                  "Ich liebe Margot",
                  "Je t'aime Marie",
                  "Te amo Maria"):

    if m := re.match(r"I love (\w+)", statement):
        print("He loves", m.group(1))

    elif m := re.match(r"Ich liebe (\w+)", statement):
        print("Er liebt", m.group(1))

    elif m := re.match(r"Je t'aime (\w+)", statement):
        print("Il aime", m.group(1))

    else:
        print()

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