如何简洁地创建一个临时文件，它是python中另一个文件的副本

Question

我知道可以创建一个临时文件，并将要复制的文件的数据写入其中。我只是想知道是否有这样的功能：

create_temporary_copy(file_path)

Answer 1

没有一个是直接的，但是可以使用tempfile和shutil.copy2的组合来实现相同的结果：

import tempfile, shutil, os
def create_temporary_copy(path):
    temp_dir = tempfile.gettempdir()
    temp_path = os.path.join(temp_dir, 'temp_file_name')
    shutil.copy2(path, temp_path)
    return temp_path

不过，您需要处理删除调用者中的临时文件。

Answer 2

这不太简洁，我想可能存在异常安全问题（例如，如果“original_path”不存在，或者当您打开文件时临时的_copy对象超出范围，会发生什么情况），但是这段代码会为清理添加一点RAII。这里直接使用NamedTemporaryFile的不同之处在于，您最终得到的不是一个file对象，而是一个偶尔需要的文件（例如，如果您计划调用其他代码来读取它，或者类似的文件）

import os,shutil,tempfile
class temporary_copy(object):

    def __init__(self,original_path):
        self.original_path = original_path

    def __enter__(self):
        temp_dir = tempfile.gettempdir()
        base_path = os.path.basename(self.original_path)
        self.path = os.path.join(temp_dir,base_path)
        shutil.copy2(self.original_path, self.path)
        return self.path

    def __exit__(self,exc_type, exc_val, exc_tb):
        os.remove(self.path)

在你的代码中你会写：

with temporary_copy(path) as temporary_path_to_copy:
    ... do stuff with temporary_path_to_copy ...

# Here in the code, the copy should now have been deleted.

Answer 3

对@tramdas的回答的一种变体，解释了在windows上文件不能打开两次的事实。此版本忽略文件扩展名的保留。

import os, shutil, tempfile

def create_temporary_copy(src):
  # create the temporary file in read/write mode (r+)
  tf = tempfile.TemporaryFile(mode='r+b', prefix='__', suffix='.tmp')

  # on windows, we can't open the the file again, either manually
  # or indirectly via shutil.copy2, but we *can* copy
  # the file directly using file-like objects, which is what
  # TemporaryFile returns to us.
  # Use `with open` here to automatically close the source file
  with open(src,'r+b') as f:
    shutil.copyfileobj(f,tf)

  # display the name of the temporary file for diagnostic purposes
  print 'temp file:',tf.name

  # rewind the temporary file, otherwise things will go
  # tragically wrong on Windows
  tf.seek(0) 
  return tf

# make a temporary copy of the file 'foo.txt'
name = None

with create_temporary_copy('foo.txt') as temp:
  name = temp.name

  # prove that it exists
  print 'exists', os.path.isfile(name) # prints True

  # read all lines from the file
  i = 0
  for line in temp:
    print i,line.strip()
    i += 1

  # temp.close() is implicit using `with`

# prove that it has been deleted
print 'exists', os.path.isfile(name) # prints False