在python中等效于grep -B的代码是什么？

概述参见英文答案 > cat, grep and cut – translated to python                                    5个 如何使用python从文件中的匹配字符串之前打印n行？ man grep -B NUM, –before-context=NUM Print NUM lines of leading context before match 参见英文答案 > cat,grep and cut – translated to python                                    5个
如何使用python从文件中的匹配字符串之前打印n行？

man grep

-B NUM,–before-context=NUM

Print NUM lines of leading context before matching lines. Places a
line containing a group separator (–) between contiguous groups of
matches. With the -o or –only-matching option,this has no effect and
a warning is given.

我有grep -A的代码：

def grepA(word,file,num=0):    with open(file) as f:        for line in f:            if word in line:                print(line + ''.join(islice(file,num)))                print('---')

解决方法 您只需要保留N个最后一行的缓冲区(列表),然后在遇到匹配时打印它们.

context_lines = []for line in f:    context_lines.append(line)    if len(context_lines) > 5:  # Too many lines?        context_lines.pop(0)  # Pop the first one off.    if word in line:        # context_lines already includes the `line` we're looking at        for ctx_line in context_lines:               print(ctx_line)

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