Question

对不起伙计们！对不起。我是Python的初学者。我正在编写以下代码：

for line in file:
 if StartingMarker in line:
  # Here: I want to push back 'line' back in 'file'
    for nextline in file:
     if EndingMarker in line:
        # Do some Operation
print "Done"

如何将'line'推回'file'？

先谢谢。

Answer 1

不要退缩，屈服。

def starttoend(it):
  for line in it:
    if 'START' in line:
      yield line
      break
  for line in it:
    yield line
    if 'END' in line:
      break

l = ['asd', 'zxc', 'START123', '456789', 'qwertyEND', 'fgh', 'cvb']

i = iter(l)
for line in starttoend(i):
  print line

如果需要更多序列，请再次使用迭代器。

Answer 2

我知道没有迭代器你可以开始迭代，然后推送一个已被带回迭代器的项目。但是你可以做的是创建一个新的迭代器（带有itertools.chain），迭代当前项和原始迭代器中的其余项。类似的东西：

import itertools

with open('some-input-file') as f:
    it = iter(f)
    for line in it:
        if StartingMarker in line:
            it2 = itertools.chain(iter([line]), it)
            for nextline in it2:
                if EndingMarker in nextline:
                    # Do some Operation

Answer 3

for line in file:
    if StartingMarker in line and EndingMarker in line:
        # look ma! no need to push back

编辑：

for line in file:
    if StartingMarker in line:
        # do some operation
        if EndingMarker in line:
            # do some other operation

Answer 4

for line in file:
    if StartingMarker in line:
        if endingmarker in line:
            #do operation
        else:
            for nextline in file:
                if EndingMarker in line:
                     # Do some Operation
print "Done"

像python中的函数一样推回？

4 个答案: