Implement touch using Python?

This tries to be a little more race-free than the other solutions. (The with keyword is new in Python 2.5.)

import os
def touch(fname, times=None):
    with open(fname, 'a'):
        os.utime(fname, times)

Roughly equivalent to this.

import os
def touch(fname, times=None):
    fhandle = open(fname, 'a')
    try:
        os.utime(fname, times)
    finally:
        fhandle.close()

Now, to really make it race-free, you need to use futimes and change the timestamp of the open filehandle, instead of opening the file and then changing the timestamp on the filename (which may have been renamed). Unfortunately, Python doesn't seem to provide a way to call futimes without going through ctypes or similar...

EDIT

As noted by Nate Parsons, Python 3.3 will add specifying a file descriptor (when os.supports_fd) to functions such as os.utime, which will use the futimes syscall instead of the utimes syscall under the hood. In other words:

import os
def touch(fname, mode=0o666, dir_fd=None, **kwargs):
    flags = os.O_CREAT | os.O_APPEND
    with os.fdopen(os.open(fname, flags=flags, mode=mode, dir_fd=dir_fd)) as f:
        os.utime(f.fileno() if os.utime in os.supports_fd else fname,
            dir_fd=None if os.supports_fd else dir_fd, **kwargs)

def touch(fname):
    if os.path.exists(fname):
        os.utime(fname, None)
    else:
        open(fname, 'a').close()

For a more low-level solution one can use

os.close(os.open("file.txt", os.O_CREAT))

Simplistic:

def touch(fname):
    open(fname, 'a').close()
    os.utime(fname, None)

• The open ensures there is a file there
• the utime ensures that the timestamps are updated

Theoretically, it's possible someone will delete the file after the open, causing utime to raise an exception. But arguably that's OK, since something bad did happen.

The following is sufficient:

import os
def func(filename):
    if os.path.exists(filename):
        os.utime(filename)
    else:
        with open(filename,'a') as f:
            pass

If you want to set a specific time for touch, use os.utime as follows:

os.utime(filename,(atime,mtime))

Here, atime and mtime both should be int/float and should be equal to epoch time in seconds to the time which you want to set.

Complex (possibly buggy):

def utime(fname, atime=None, mtime=None)
    if type(atime) is tuple:
        atime, mtime = atime

    if atime is None or mtime is None:
        statinfo = os.stat(fname)
        if atime is None:
            atime = statinfo.st_atime
        if mtime is None:
            mtime = statinfo.st_mtime

    os.utime(fname, (atime, mtime))


def touch(fname, atime=None, mtime=None):
    if type(atime) is tuple:
        atime, mtime = atime

    open(fname, 'a').close()
    utime(fname, atime, mtime)

This tries to also allow setting the access or modification time, like GNU touch.

Why don't you try: newfile.py

#!/usr/bin/env python
import sys
inputfile = sys.argv[1]

with open(inputfile, 'r+') as file:
    pass

python newfile.py foobar.txt

or

use subprocess:

import subprocess
subprocess.call(["touch", "barfoo.txt"])

write_text() from pathlib.Path can be used.

>>> from pathlib import Path
>>> Path('aa.txt').write_text("")
0

There is also a python module for touch

>>> from touch import touch
>>> touch(file_name)

You can install it with pip install touch