Question

我正在使用一个加密文件，但是我无法用for创建一个循环以便在关闭并删除它之前对其进行读取。

我的意图是读取加密文件中给出的数据，并将其循环以将每一行分配给一个变量。

每当我执行我的代码时，Python都会直接完成，而不使用解密的信息。我相信是因为with命令在循环开始之前将其关闭。

这就是我想要的，不起作用，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)

这是有效的代码（对不起，试图使其更短但不能）：

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)

两个示例的标题（为了简短起见）：

#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

有任何提示吗？

Answer 1

问题在于，一旦您写入文件，“文件指针”就位于文件的末端。什么都没读。

您可以使用seek method重新定位文件指针的开头。另外，关闭并重新打开文件（如在工作代码中一样）会将指针定位在文件的开头。

Answer 2

@LarryLustig几乎回答了为什么您的代码不起作用，但是IMO如果您完全消除了temp文件（这不是必需的），则您甚至不必担心光标。请参阅以下对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），则可以完全不使用os.linesep。

如何在临时文件中使用FOR创建循环？

2 个答案: