出于所有意图和目的，我是Python用户并且每天使用Pandas库。正则表达式中的命名捕获组非常有用。因此，例如，提取特定单词或短语的出现并在数据帧的新列中生成结果的连接字符串是相对微不足道的。下面给出了如何实现这一目标的一个例子：
import numpy as np
import pandas as pd
import re
myDF = pd.DataFrame(['Here is some text',
'We all love TEXT',
'Where is the TXT or txt textfile',
'Words and words',
'Just a few works',
'See the text',
'both words and text'],columns=['origText'])
print("Original dataframe\n------------------")
print(myDF)
# Define regex to find occurrences of 'text' or 'word' as separate named groups
myRegex = """(?P<textOcc>t[e]?xt)|(?P<wordOcc>word)"""
myCompiledRegex = re.compile(myRegex,flags=re.I|re.X)
# Extract all occurrences of 'text' or 'word'
myMatchesDF = myDF['origText'].str.extractall(myCompiledRegex)
print("\nDataframe of matches (with multi-index)\n--------------------")
print(myMatchesDF)
# Collapse resulting multi-index dataframe into single rows with concatenated fields
myConcatMatchesDF = myMatchesDF.groupby(level = 0).agg(lambda x: '///'.join(x.fillna('')))
myConcatMatchesDF = myConcatMatchesDF.replace(to_replace = "^/+|/+$",value = "",regex = True) # Remove '///' at start and end of strings
print("\nCollapsed and concatenated matches\n----------------------------------")
print(myConcatMatchesDF)
myDF = myDF.join(myConcatMatchesDF)
print("\nFinal joined dataframe\n----------------------")
print(myDF)
这会产生以下输出：
Original dataframe
------------------
origText
0 Here is some text
1 We all love TEXT
2 Where is the TXT or txt textfile
3 Words and words
4 Just a few works
5 See the text
6 both words and text
Dataframe of matches (with multi-index)
--------------------
textOcc wordOcc
match
0 0 text NaN
1 0 TEXT NaN
2 0 TXT NaN
1 txt NaN
2 text NaN
3 0 NaN Word
1 NaN word
5 0 text NaN
6 0 NaN word
1 text NaN
Collapsed and concatenated matches
----------------------------------
textOcc wordOcc
0 text
1 TEXT
2 TXT///txt///text
3 Word///word
5 text
6 text word
Final joined dataframe
----------------------
origText textOcc wordOcc
0 Here is some text text
1 We all love TEXT TEXT
2 Where is the TXT or txt textfile TXT///txt///text
3 Words and words Word///word
4 Just a few works NaN NaN
5 See the text text
6 both words and text text word
我已经打印过每一个阶段，试图让它易于理解。
问题是，我可以在R中做类似的事情吗？我已经在网上搜索但是找不到任何描述使用命名组的内容（虽然我是一个R-newcomer和所以可能会搜索错误的库或描述性术语。）
我已经能够识别包含一个或多个匹配项的项目，但我看不到如何提取特定匹配项或如何使用命名组。到目前为止我使用的代码（使用与上面Python示例相同的数据框和正则表达式）是：
origText = c('Here is some text','We all love TEXT','Where is the TXT or txt textfile','Words and words','Just a few works','See the text','both words and text')
myDF = data.frame(origText)
myRegex = "(?P<textOcc>t[e]?xt)|(?P<wordOcc>word)"
myMatches = grep(myRegex,myDF$origText,perl=TRUE,value=TRUE,ignore.case=TRUE)
myMatches
[1] "Here is some text" "We all love TEXT" "Where is the TXT or txt textfile" "Words and words"
[5] "See the text" "both words and text"
myMatchesRow = grep(myRegex,myDF$origText,perl=TRUE,value=FALSE,ignore.case=TRUE)
myMatchesRow
[1] 1 2 3 4 6 7
正则表达式似乎正在工作，并且正确的行被标识为包含匹配（即，除了上面示例中的第5行之外的所有行）。但是，我的问题是，我是否可以生成类似于Python生成的输出，其中提取特定匹配项并在数据框中使用正则表达式中包含的组名命名的新列中列出？
答案 0 :(得分：5)
Base R确实捕获了有关名称的信息，但它没有一个好帮手来按名称提取它们。我写了一个包装来帮助调用regcapturedmatches。您可以将其与
一起使用myRegex = "(?<textOcc>t[e]?xt)|(?<wordOcc>word)"
m<-regexpr(myRegex, origText, perl=T, ignore.case=T)
regcapturedmatches(origText,m)
返回
textOcc wordOcc
[1,] "text" ""
[2,] "TEXT" ""
[3,] "TXT" ""
[4,] "" "Word"
[5,] "" ""
[6,] "text" ""
[7,] "" "word"