Open explorer on a file

A nicer and safer solution (only in Windows unfortunately) is os.startfile().

When it's given a folder instead of a file, it will open Explorer.

Im aware that i do not completely answer the question since its not selecting a file, but using subprocess is always kind of a bad idea (for security reasons) and this solution may help other people.

Alternatively, you could use the fileopenbox module of EasyGUI to open the file explorer for the user to click through and then select a file (returning the full filepath).

import easygui
file = easygui.fileopenbox()

As explorer could be overridden it would be a little safer to point to the executable directly. (just had to be schooled on this too)

And while you're at it: use Python 3s current subprocess API: run()

import os
import subprocess
FILEBROWSER_PATH = os.path.join(os.getenv('WINDIR'), 'explorer.exe')

def explore(path):
    # explorer would choke on forward slashes
    path = os.path.normpath(path)

    if os.path.isdir(path):
        subprocess.run([FILEBROWSER_PATH, path])
    elif os.path.isfile(path):
        subprocess.run([FILEBROWSER_PATH, '/select,', path])

From Geoff Chappell's The Windows Explorer Command Line

import subprocess
subprocess.Popen(r'explorer /select,"C:\path\of\folder\file"')