Python:在关键字前后抓取文本

keywords = ("banana", "apple", "orange", ...) 
before = 50 
after = 100 
TEXT = "a big text string,  i.e., a page of a book" 
 
for k in keywords: 
    if k in TEXT: 
        #cut = portion of text starting 'beforeText' chars before occurrence of 'k' and ending 'afterText' chars after occurrence of 'k' 
        #finalcut = 'cut' with first and last WORDS trimmed to assure starting words are not cut in the middle 

伙计们，你能帮我编写上面例子中的 cut 和 finalcut 字符串变量吗？

考虑到我要处理大文本、大量页面和可能超过 20 个要搜索的关键字，最有效的解决方案是什么？

请您参考如下方法:

您可以使用 re.finditer 查找字符串中的所有匹配项.每个匹配对象都有一个 start()方法可以用来计算字符串中的位置。您也不需要检查键是否在字符串中，因为 finditer 会返回一个空迭代器:

keywords = ("banana", "apple", "orange", ...) 
before = 50 
after = 100 
TEXT = "a big text string,  i.e., a page of a book" 
 
for k in keywords: 
    for match in re.finditer(k, TEXT): 
        position = match.start() 
        cut = TEXT[max(position - before, 0):position + after] # max is needed because that index must not be negative 
        trimmed_match = re.match("\w*?\W+(.*)\W+\w*", cut, re.MULTILINE) 
        finalcut = trimmed_match.group(1) 

正则表达式修剪所有内容，包括第一个非单词字符序列和最后一个非单词字符序列(我添加了 re.MULTILINE 以防换行在你的文字中)