A simple command line tool for managing windows PATH variable in Windows Registry. Get help by `python winpath.py help`.

winpath.py

'''
A simple command line tool for managing windows PATH variable.
'''
import _winreg as winreg
import os
import sys


def choose_key(scope, write=False):
    '''
    Choose the winreg key.
    '''
    param = []
    if scope == 'user':
        param = [winreg.HKEY_CURRENT_USER,
                 "Environment"]
    elif scope == 'system':
        param = [winreg.HKEY_LOCAL_MACHINE,
                 "SYSTEM\CurrentControlSet\Control\Session Manager\Environment"]
    else:
        raise Exception('Unknown scope %s.' % scope)
    if write:
        param.extend([0, winreg.KEY_ALL_ACCESS]) 
    return winreg.OpenKey(*param)


def get_path(scope):
    '''
    Get the PATH variable content w.r.t. the scope.
    '''
    key = choose_key(scope)
    path = winreg.QueryValueEx(key, 'path')[0]
    return path.strip()


def display_path(path):
    '''
    Split the PATH variable by ; and output.
    '''
    for i in path.split(';'):
        print i


class PathOp(object):
    @classmethod
    def list(cls, scope=None):
        '''
        list [scope]
        scope could be user or system, which will list
        the paths from current user or system variables.
        If scope is omitted, both user and system paths
        will be listed.
        '''
        scope = ['user', 'system'] if scope is None else [scope]
        for s in scope:
            display_path(get_path(s))

    @classmethod
    def find(cls, target_path):
        '''
        find target_path
        Find the target_path in user/system paths.
        '''
        for scope in ['user', 'system']:
            path = get_path(scope)
            if target_path.lower() in path.lower():
                print "Find %s in %s path" % (target_path, scope)

    @classmethod
    def add(cls, scope, target_path):
        '''
        add scope target_path
        Add target_path in specfied scope.
        The scope could be user or system
        '''
        current_path = get_path(scope)
        if target_path.lower() in current_path.lower():
            print "%s is already in the PATH." % target_path
            return
        key = choose_key(scope, write=True)
        current_path = (current_path + ';') if not current_path.endswith(';') else current_path
        new_path = current_path + target_path
        winreg.SetValueEx(key, "path", 0, winreg.REG_EXPAND_SZ, new_path)
        print "Add %s in %s path." % (target_path, scope)

    @classmethod
    def remove(cls, target_path):
        '''
        remove target_path
        Remove the target_path from user/system paths.
        '''
        for scope in ['user', 'system']:
            path = get_path(scope)
            if target_path.lower() in path.lower():
                index = path.lower().find(target_path.lower())
                new_path = path[:index] + path[index+len(target_path):]
                new_path = new_path.replace(';;', ';')
                key = choose_key(scope, write=True)
                winreg.SetValueEx(key, "path", 0, winreg.REG_EXPAND_SZ, new_path)
                print 'Remove %s in %s path.' % (target_path, scope)

    @classmethod
    def help(cls, command=None):
        if command is None:
            print "winpath.py is a simple tool to manage your PATH"
            print "Usage:"
            print "python winpath.py cmd [options]"
            print "cmd may be list, find, add, remove"
            print "Use"
            print "python winpath.py help cmd"
            print "to get detail help of a command."
            print "If you gonna change system paths, Administrator permission is required."
        else:
            if command in ('list', 'find', 'add', 'remove'):
                print getattr(cls, command).__doc__


def main():
    if len(sys.argv)<2:
        PathOp.help()
        sys.exit(0)
    cmd = sys.argv[1]
    if hasattr(PathOp, cmd):
        getattr(PathOp, cmd)(*sys.argv[2:])

if __name__ == '__main__':
    main()

Great tool @socrateslee, exactly what I was looking for. Thanks a lot!