def _prefix_env_vars(command, local=False):
    """
    Prefixes ``command`` with any shell environment vars, e.g. ``PATH=foo ``.

    Currently, this only applies the PATH updating implemented in
    `~fabric.context_managers.path` and environment variables from
    `~fabric.context_managers.shell_env`.

    Will switch to using Windows style 'SET' commands when invoked by
    ``local()`` and on a Windows localhost.
    """
    env_vars = {}

    # path(): local shell env var update, appending/prepending/replacing $PATH
    path = env.path
    if path:
        if env.path_behavior == 'append':
            path = '$PATH:\"%s\"' % path
        elif env.path_behavior == 'prepend':
            path = '\"%s\":$PATH' % path
        elif env.path_behavior == 'replace':
            path = '\"%s\"' % path

        env_vars['PATH'] = path

    # shell_env()
    env_vars.update(env.shell_env)

    if env_vars:
        set_cmd, exp_cmd = '', ''
        if win32 and local:
            set_cmd = 'SET '
        else:
            exp_cmd = 'export '

        exports = ' '.join(
            '%s%s="%s"' % (set_cmd, k, v if k == 'PATH' else _shell_escape(v))
            for k, v in env_vars.iteritems()
        )
        shell_env_str = (exp_cmd, exports) % '%s%s && '
    else:
        shell_env_str = ''

    return shell_env_str + command
dataset/ETHPy150Open fabric/fabric/fabric/operations.py/_prefix_env_vars/swapped operands of `%`