how to concisely create a temporary file that is a copy of another file in python

Question

I know that it is possible to create a temporary file, and write the data of the file I wish to copy to it. I was just wondering if there was a function like:

create_temporary_copy(file_path)

Answer 1

There isn't one directly, but you can use a combination of tempfile and shutil.copy2 to achieve the same result:

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

You'll need to deal with removing the temporary file in the caller, though.

Answer 2

This isn't quite as concise, and I imagine there may be issues with exception safety, (e.g. what happens if 'original_path' doesn't exist, or the temporary_copy object goes out of scope while you have the file open) but this code adds a little RAII to the clean up. The difference here to using NamedTemporaryFile directly is that rather than ending up with a file object, you end up with a file, which is occasionally desirable (e.g. if you plan to call out to other code to read it, or some such.)

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)

in your code you'd write:

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

A variation on @tramdas's answer, accounting for the fact that the file cannot be opened twice on windows. This version ignores the preservation of the file extension.

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

Answer 4

The following is more concise (OP's ask) than the selected answer. Enjoy!

import tempfile, shutil, os
def create_temporary_copy(path):
  tmp = tempfile.NamedTemporaryFile(delete=True)
  shutil.copy2(path, tmp.name)
  return tmp.name

Answer 5

A slight variation (in particular I needed the preserve_extension feature for my use case, and I like the "self-cleanup" feature):

import os, shutil, tempfile
def create_temporary_copy(src_file_name, preserve_extension=False):
    '''
    Copies the source file into a temporary file.
    Returns a _TemporaryFileWrapper, whose destructor deletes the temp file
    (i.e. the temp file is deleted when the object goes out of scope).
    '''
    tf_suffix=''
    if preserve_extension:
        _, tf_suffix = os.path.splitext(src_file_name)
    tf = tempfile.NamedTemporaryFile(suffix=tf_suffix)
    shutil.copy2(src_file_name, tf.name)
    return tf