Question

我正在制作一个从网站获取数据然后将其记录在文本文件中的python程序。我希望这能记录最后1000个（我正在测试4和一个字符串“hello”）条目并删除其余部分。以下是我到目前为止的情况：

f = open("test.txt", "r")
text = f.read()

f = open("test.txt", "w")
content = text.splitlines(True)
f.write("hello")
f.write("\n")

for x in range(0,4):
    f.write(str(content[x:x+1]).strip('[]'))

f.close()

然而，“工作”会将文本文件格式化为：

hello
'hello\n''\'hello\\n\'\'\\\'hello\\\\n\\\'\\\'\\\\\\\'hello\\\\\\\\n\\\\\\\'"\\\\\\\'hello\\\\\\\\\\\\\\\\n\\\\\\\'"\\\'\''

你能帮我解决这个问题，看起来像这样：

hello
hello
hello
hello

谢谢！

Answer 1

使用deque，因为它提供了maxlen。添加行/单词将只保留maxlen项目，新项目将被添加，旧项目将被遗忘。

from collections import deque
fname = "source.txt"
last_lines = deque(maxlen = 4)
with open(fname) as f:
  text = f.read()
  for line in text.splitlines(True):
    last_lines.append(line)
#f is closed when we leave the block 

outfname = fname
with open(outfname, "w") as of:
  for line in last_lines:
    of.write(line)

即使没有分割线也可以这样做（但你要求它）。

from collections import deque
fname = "source.txt"
last_lines = deque(maxlen = 4)
for line in open(fname):
  last_lines.append(line)
#file is closed when we leave the (for) block

outfname = fname
with open(outfname, "w") as of:
  for line in last_lines:
    of.write(line)

使用Jon Clements的技巧（使用文件描述符创建的迭代器创建deque）并允许自己使用不同的源文件和目标文件，它可以变得非常简短：

from collections import deque
with open("target.txt", "w") as out_f:
  for line in deque(open("source.txt"), maxlen = 4):
    out_f.write(line)

Python：从文本文件中splitlines（）然后将它们写回文本文件

1 个答案: