Fixes python's PATH entries on Windows. Run as Administrator.

fix_python.py

# coding: utf-8
'''
Fixes python's PATH entries on Windows. Run as Administrator.

https://stackoverflow.com/users/1307905/anthon

fixed by https://stackoverflow.com/users/19993/aur-saraf
'''

import sys
import os
import time
import _winreg
import ctypes

def find_python():
    """
    retrieves the commandline for .py extensions from the registry
    """
    hKey = _winreg.OpenKey(_winreg.HKEY_CLASSES_ROOT,
                           r'Python.File\shell\open\command')
    # get the default value
    value, typ = _winreg.QueryValueEx (hKey, None)
    program = value.split('"')[1]
    if not program.lower().endswith(r'\python.exe'):
        return None
    return os.path.dirname(program)

def extend_path(pypath, remove=False, verbose=0, script=False):
    """
    extend(pypath) adds pypath to the PATH env. variable as defined in the
    registry, and then notifies applications (e.g. the desktop) of this change.
    !!! Already opened DOS-Command prompts are not updated. !!!
    Newly opened prompts will have the new path (inherited from the 
    updated windows explorer desktop)
    options:
    remove (default unset), remove from PATH instead of extend PATH
    script (default unset), try to add/remove the Scripts subdirectory 
        of pypath (pip, easy_install) as well
    """
    _sd = 'Scripts' # scripts subdir
    scriptspath = os.path.join(pypath, _sd)
    hKey = _winreg.OpenKey (_winreg.HKEY_LOCAL_MACHINE,
               r'SYSTEM\CurrentControlSet\Control\Session Manager\Environment',
               0, _winreg.KEY_READ | _winreg.KEY_SET_VALUE)

    value, typ = _winreg.QueryValueEx (hKey, "PATH")
    vals = value.split(';')
    assert isinstance(vals, list)
    lowervals = value.lower().split(';')
    def already_exists(v):
        v = v.lower()
        for val in lowervals:
            if val in [v, v + os.path.pathsep]:
                return True
        return False
    if remove:
        try:
            vals.remove(pypath)
        except ValueError:
            if verbose > 0:
                print 'path element', pypath, 'not found'
            return
        if script:
            try:
                vals.remove(scriptspath)
            except ValueError:
                pass
            print 'removing from PATH:', pypath
    else:
        if not already_exists(pypath):
            if verbose > 0:
                print 'path element', pypath, 'already in PATH'
        else:
            vals.append(pypath)
            if verbose > 1:
                print 'adding to PATH:', pypath
        if script:
            if not already_exists(scriptspath):
                vals.append(scriptspath)
                if verbose > 1:
                    print 'adding to PATH:', scriptspath
    return
    _winreg.SetValueEx(hKey, "OLDPATH", 0, typ, value )
    _winreg.SetValueEx(hKey, "PATH", 0, typ, ';'.join(vals) )
    _winreg.FlushKey(hKey)
    # notify other programs
    SendMessage = ctypes.windll.user32.SendMessageW
    HWND_BROADCAST = 0xFFFF
    WM_SETTINGCHANGE = 0x1A
    SendMessage(HWND_BROADCAST, WM_SETTINGCHANGE, 0, u'Environment')
    if verbose > 1:
        print 'Do not forget to restart any command prompts'

if __name__ == '__main__':
    remove = '--remove' in sys.argv
    script = '--noscripts' not in sys.argv
    extend_path(find_python(), verbose=2, remove=remove, script=script)