如何在临时文件中使用 FOR 创建循环？

Question

我正在处理一个加密文件，但我无法使用 for 创建一个循环以便在它被关闭和删除之前读取它。

我的目的是读取加密文件中给出的数据并循环它以将每一行分配给一个变量。

每当我执行我的代码时，Python 直接完成，不处理解密的信息；我相信这是因为 with 命令在循环开始之前关闭它。

这就是我想要的，不工作，也没有错误：

with open(input_file, 'rb') as fp:
  data = fp.read()

fernet = Fernet(key)
encrypted = fernet.decrypt(data)
with tempfile.TemporaryFile() as fp:
  fp.write(encrypted)
  for url in fp: #Python ignores the tempfile. I belive it is closed in the previous line.
    segment = url.strip()
    url = 'https://docs.python.org/3.3/tutorial/' + segment
    filename = segment + '.html'
    filePath = pjoin('Data/' + filename)
    response = urlopen(url)
    webContent = response.read()
    html_content = urlopen(url).read()
    matches = re.findall(b'string', html_content);

    if len(matches) == 0: 
      print(segment + ' unchanged.')

    else:  
      with open(filePath, 'wb') as w:
       w.write(webContent)

这是工作代码（抱歉，试图缩短但不能）：

with open(input_file, 'rb') as fp:
  data = fp.read()

fernet = Fernet(key)
encrypted = fernet.decrypt(data)

with open(output_file, 'wb') as fp:
    fp.write(encrypted)

with open(output_file) as fp:
    for url in fp:
      segment = url.strip()
      url = 'https://docs.python.org/3.3/tutorial/' + segment
      filename = segment + '.html'
      filePath = pjoin('Data/' + filename)
      response = urlopen(url)
      webContent = response.read()
      html_content = urlopen(url).read()
      matches = re.findall(b'string', html_content);

    if len(matches) == 0: 
      print(segment + ' unchanged.')

    else:  
      with open(filePath, 'wb') as w:
       w.write(webContent)

Header 两个例子（除了缩短）：

#python 3.6.6

from urllib.request import urlopen
import urllib.request
from os.path import join as pjoin
import re, os, sys, tempfile, six, ctypes, time, fileinput
from cryptography.fernet import Fernet

print("[*] Checking list.dat for consistency . . .")
key = b'wTmVBRLytAmlfkctCuEf59K0LDCXa3sGas3kPg3r4fs=' #Decrypt list.dat
input_file = 'List.dat'
output_file = 'List.txt'

List.txt内容：

errors
classes
stdlib

有什么提示吗？

Answer 1

问题是，一旦您写入文件，"file pointer" 就位于文件的末尾。没什么可看的

您可以使用seek method 将文件指针重新定位在开头。或者，关闭并重新打开文件（如在您的工作代码中一样）会将指针定位在文件的开头。

Answer 2

@LarryLustig 几乎回答了为什么 你的代码没有工作，但在我看来，如果你完全删除临时文件（这不是必需的）你甚至没有需要担心光标。请参阅下面对您所需代码的评论更改。

# We'll use os.linesep to get the line terminator string for your os.
import os

...

with open(input_file, 'rb') as fp:
  data = fp.read()

fernet = Fernet(key)

# decode your decrypted bytes into strings.  Change 'utf-8' into whichever file encoding you're using if necessary.
decrypted = fernet.decrypt(data).decode('utf-8')

# Don't write to a temp file
# Iterate directly on each line of the extracted data
for url in decrypted.split(os.linesep): 
    segment = url.strip()
    url = 'https://docs.python.org/3.3/tutorial/' + segment
    filename = segment + '.html'
    filePath = pjoin('Data/' + filename)
    response = urlopen(url)
    webContent = response.read()
    html_content = urlopen(url).read()
    matches = re.findall(b'string', html_content);

    if len(matches) == 0: 
      print(segment + ' unchanged.')

    else:  
      with open(filePath, 'wb') as w:
       w.write(webContent)

或者，如果您确定文件中使用的行终止符是什么（例如 \r\n 或 \n），那么您可以完全避免使用 os.linesep。

如何在临时文件中使用 FOR 创建循环？

How to create a loop with FOR in a temporary file?

python

python-3.x

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temp