Question

我不是在谈论具体的行号，因为我正在阅读具有相同格式但长度不同的多个文件说我有这个文本文件：

Something here...  
... ... ...   
Start                      #I want this block of text 
a b c d e f g  
h i j k l m n  
End                        #until this line of the file
something here...  
... ... ...

我希望你知道我的意思。我正在考虑迭代文件，然后使用正则表达式搜索，找到“开始”和“结束”的行号，然后使用linecache从开始行读取到结束行。但是如何获得行号？我可以使用什么功能？

Answer 1

如果您只想要Start和End之间的文字块，您可以做一些简单的事情：

with open('test.txt') as input_data:
    # Skips text before the beginning of the interesting block:
    for line in input_data:
        if line.strip() == 'Start':  # Or whatever test is needed
            break
    # Reads text until the end of the block:
    for line in input_data:  # This keeps reading the file
        if line.strip() == 'End':
            break
        print line  # Line is extracted (or block_of_lines.append(line), etc.)

实际上，您无需操纵行号就可以读取开始和结束标记之间的数据。

逻辑（“读取直到......”）在两个块中重复，但它非常清晰有效（其他方法通常涉及检查某些状态[在块/块内/块到达之前]，这会产生一些时间罚分）。

Answer 2

这是可行的：

data_file = open("test.txt")
block = ""
found = False

for line in data_file:
    if found:
        block += line
        if line.strip() == "End": break
    else:
        if line.strip() == "Start":
            found = True
            block = "Start"

data_file.close()

Answer 3

你可以很容易地使用正则表达式。您可以根据需要使其更加健壮，下面是一个简单的示例。

>>> import re
>>> START = "some"
>>> END = "Hello"
>>> test = "this is some\nsample text\nthat has the\nwords Hello World\n"
>>> m = re.compile(r'%s.*?%s' % (START,END), re.S)
>>> m.search(test).group(0)
'some\nsample text\nthat has the\nwords Hello'

Answer 4

这应该是你的开始：

started = False
collected_lines = []
with open(path, "r") as fp:
     for i, line in enumerate(fp.readlines()):
         if line.rstrip() == "Start": 
             started = True
             print "started at line", i # counts from zero !
             continue
          if started and line.rstrip()=="End":
             print "end at line", i
             break
          # process line 
          collected_lines.append(line.rstrip())

enumerate生成器接受生成器并枚举迭代。例如

  print list(enumerate("a b c".split()))

打印

   [ (0, "a"), (1,"b"), (2, "c") ]

<强>更新：

海报要求使用正则表达式来匹配“===”和“======”之类的行：

import re
print re.match("^=+$", "===")     is not None
print re.match("^=+$", "======")  is not None
print re.match("^=+$", "=")       is not None
print re.match("^=+$", "=abc")    is not None
print re.match("^=+$", "abc=")    is not None

python - 从特定文本行读取文件

4 个答案: