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

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 4

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 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

Answer 6

You can try this to create a temporary file and then a copy. I like to set delete=False in case I need to do something to the temp file before creating the copy. The temp file is then closed manually and thus deleted:

import shutil, tempfile, os
temp_file = tempfile.NamedTemporaryFile(mode='w', suffix='.txt', delete=False)
#Do something to temp file
shutil.copyfile('copy_name.txt', temp_file.name)
temp_file.close()

Answer 7

I wanted a more generic context manager which can copy files to the temp dir. In case this helps anyone with this issue:

from contextlib import contextmanager
from pathlib import Path
from shutil import copytree
from tempfile import TemporaryDirectory
from typing import Iterator

@contextmanager
def temporary_directory(source_dir: Path | None = None) -> Iterator[Path]:
    """Create a tempory directory for use within this context, yield its path, and purge on exit.

    Args:
        source_dir (Path | None, optional): A path to a directory to copy to the temporary
            directory. Defaults to None.

    Raises:
        FileNotFoundError: Raised if source_dir is passed but does not exist or was not found.
        ValueError: Raised if source_dir is passed but is to a file, not a directory.

    Yields:
        Iterator[Path]: The path to the temporary directory with the source directory
            files within it.
    """
    if source_dir is not None and not source_dir.exists():
        raise FileNotFoundError(f"{source_dir!s} does not exist")
    if source_dir is not None and not source_dir.is_dir():
        raise ValueError(f"{source_dir!s} is not a directory")
    with TemporaryDirectory() as temp_dir:
        if source_dir is not None:
            copytree(source_dir, temp_dir, dirs_exist_ok=True)
        yield Path(temp_dir).absolute()