python - How to grab a chunk of data from a file? -

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i want grab chunk of data file. know start line , end line. wrote code incomplete , don't know how solve further. 

file = open(filename,'r')     end_line='### leave comment!' star_line = 'kill master'     line in file:             if star_line in line:            ?? 

startmarker = "ohai" endmarker = "meheer?" marking = false result = []  open("somefile") f:   line in f:     if line.startswith(startmarker): marking = true     elif line.startswith(endmarker): marking = false      if marking: result.append(line)  if len(result) > 1:   print "".join(result[1:])

explanation: with block nice way use files -- makes sure don't forget close() later. for walks each line and:

  • starts outputting when sees line starts 'ohai' (including line)
  • stops outputting when sees line starts 'meheer?' (without outputting line).

after loop, result contains part of file needed, plus initial marker. rather making loop more complicated ignore marker, throw out using slice: result[1:] returns elements in result starting @ index 1; in other words, excludes first element (index 0).

update reflect add partial-line matches:

startmarker = "ohai" endmarker = "meheer?" marking = false result = []  open("somefile") f:   line in f:     if not marking:       index = line.find(startmarker)       if index != -1:         marking = true         result.append(line[index:])     else:       index = line.rfind(endmarker)       if index != -1:         marking = false         result.append(line[:index + len(endmarker)])       else:         result.append(line)  print "".join(result)

yet more explanation: marking still tells whether should outputting whole lines, i've changed if statements start , end markers follows:

  • if we're not (yet) marking, , see startmarker, output current line starting @ marker. find method returns position of first occurrence of startmarker in case. line[index:] notation means 'the content of line starting @ position index.

  • while marking, output current line entirely unless contains endmarker. here, use rfind find rightmost occurrence of endmarker, , line[...] notation means 'the content of line position index (the start of match) plus marker itself.' also: stop marking :)


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