Question

我正在尝试提取具有特定文本文件的文本：

----
data1
data1
data1
extractme
----
data2
data2
data2
----
data3
data3
extractme
----

然后将其转储到文本文件中以便

----
data1
data1
data1
extractme
---
data3
data3
extractme
---

感谢您的帮助。

Answer 1

这对我来说效果很好。您的示例数据位于名为“data.txt”的文件中，输出将转到“result.txt”

inFile = open("data.txt")
outFile = open("result.txt", "w")
buffer = []
keepCurrentSet = True
for line in inFile:
    buffer.append(line)
    if line.startswith("----"):
        #---- starts a new data set
        if keepCurrentSet:
            outFile.write("".join(buffer))
        #now reset our state
        keepCurrentSet = False
        buffer = []
    elif line.startswith("extractme"):
        keepCurrentSet = True
inFile.close()
outFile.close()

Answer 2

我想象破折号的数量变化（输入中有4个，有时是4个，有时是输出中的3个）是一个错误，实际上并不需要（因为没有算法甚至暗示过，要解释有多少破折号）不同场合的输出）。

我会根据阅读和一次产生一个行块来构建任务：

def readbyblock(f):
  while True:
      block = []
      for line in f:
          if line = '----\n': break
          block.append(line)
      if not block: break
      yield block

这样（选择性）输出可以与输入整齐地分开：

with open('infile.txt') as fin:
    with open('oufile.txt', 'w') as fou:
        for block in readbyblock(fin):
            if 'extractme\n' in block:
                fou.writelines(block)
                fou.write('----\n')

如果块很大，这在性能方面不是最佳的，因为它在if子句中隐含的块中的所有行上都有一个单独的循环。所以，一个好的重构可能是：

def selectivereadbyblock(f, marker='extractme\n'):
  while True:
      block = []
      extract = False
      for line in f:
          if line = '----\n': break
          block.append(line)
          if line==marker: extract = True
      if not block: break
      if extract: yield block

with open('infile.txt') as fin:
    with open('oufile.txt', 'w') as fou:
        for block in selectivereadbyblock(fin):
            fou.writelines(block)
            fou.write('----\n')

参数化分隔符（现在硬编码为输入和输出的'---- \ n'）是另一种合理的编码调整。

Answer 3

对于Python2

#!/usr/bin/env python

with open("infile.txt") as infile:
    with open("outfile.txt","w") as outfile:
        collector = []
        for line in infile:
            if line.startswith("----"):
                collector = []
            collector.append(line)
            if line.startswith("extractme"):
                for outline in collector:
                    outfile.write(outline)

对于Python3

#!/usr/bin/env python3

with open("infile.txt") as infile, open("outfile.txt","w") as outfile:
    collector = []
    for line in infile:
        if line.startswith("----"):
            collector = []
        collector.append(line)
        if line.startswith("extractme"):
            for outline in collector:
                outfile.write(outline)

Answer 4

data=open("file").read().split("----")
print '----'.join([ i for i in data if "extractme" in i ])

Python从文件中提取数据

4 个答案: