下面是一个如何执行文件系统路径增量补全的快速示例。我修改了您的示例，将其组织到一个类中，其中名为complete_[name]的方法表示顶级命令。
我已经将完成函数切换为使用内部readline缓冲区来确定整个完成的状态，这使得状态逻辑简单了一些，路径完成在_complete_path(path)方法中，我已经连接了extra命令来对其参数执行路径完成。
我确信代码可以进一步简化，但它应该为您提供一个不错的起点：

import os
import re
import readline

COMMANDS = ['extra', 'extension', 'stuff', 'errors',
            'email', 'foobar', 'foo']
RE_SPACE = re.compile('.*\s+$', re.M)

class Completer(object):

    def _listdir(self, root):
        "List directory 'root' appending the path separator to subdirs."
        res = []
        for name in os.listdir(root):
            path = os.path.join(root, name)
            if os.path.isdir(path):
                name += os.sep
            res.append(name)
        return res

    def _complete_path(self, path=None):
        "Perform completion of filesystem path."
        if not path:
            return self._listdir('.')
        dirname, rest = os.path.split(path)
        tmp = dirname if dirname else '.'
        res = [os.path.join(dirname, p)
                for p in self._listdir(tmp) if p.startswith(rest)]
        # more than one match, or single match which does not exist (typo)
        if len(res) > 1 or not os.path.exists(path):
            return res
        # resolved to a single directory, so return list of files below it
        if os.path.isdir(path):
            return [os.path.join(path, p) for p in self._listdir(path)]
        # exact file match terminates this completion
        return [path + ' ']

    def complete_extra(self, args):
        "Completions for the 'extra' command."
        if not args:
            return self._complete_path('.')
        # treat the last arg as a path and complete it
        return self._complete_path(args[-1])

    def complete(self, text, state):
        "Generic readline completion entry point."
        buffer = readline.get_line_buffer()
        line = readline.get_line_buffer().split()
        # show all commands
        if not line:
            return [c + ' ' for c in COMMANDS][state]
        # account for last argument ending in a space
        if RE_SPACE.match(buffer):
            line.append('')
        # resolve command to the implementation function
        cmd = line[0].strip()
        if cmd in COMMANDS:
            impl = getattr(self, 'complete_%s' % cmd)
            args = line[1:]
            if args:
                return (impl(args) + [None])[state]
            return [cmd + ' '][state]
        results = [c + ' ' for c in COMMANDS if c.startswith(cmd)] + [None]
        return results[state]

comp = Completer()
# we want to treat '/' as part of a word, so override the delimiters
readline.set_completer_delims(' \t\n;')
readline.parse_and_bind("tab: complete")
readline.set_completer(comp.complete)
raw_input('Enter section name: ')

用法：

% python complete.py 
Enter section name: ext<tab>
extension extra
Enter section name: extra foo<tab>
foo.py foo.txt foo/
Enter section name: extra foo/<tab>
foo/bar.txt foo/baz.txt
Enter section name: extra foo/bar.txt

更新如果用户键入/，则将完成从根目录开始的路径：

% python complete.py
Enter section name: extra /Use<tab>
/Users/.localized  /Users/Shared/  /Users/user1 /Users/user2
Enter section name: extra /Users/use<tab>
/Users/user1  /Users/user2

这足以支持raw_input（）的内置目录制表符完成功能：

import readline
readline.parse_and_bind("tab: complete")

这个版本是针对python3的，使用pathlib，并且是一个用tab完成files/dirs的简约版本。它基于上面的一些答案，但是只对files/dirs有效。

#!/usr/bin/python

import pathlib
import readline

def complete_path(text, state):
    incomplete_path = pathlib.Path(text)
    if incomplete_path.is_dir():
        completions = [p.as_posix() for p in incomplete_path.iterdir()]
    elif incomplete_path.exists():
        completions = [incomplete_path]
    else:
        exists_parts = pathlib.Path('.')
        for part in incomplete_path.parts:
            test_next_part = exists_parts / part
            if test_next_part.exists():
                exists_parts = test_next_part

        completions = []
        for p in exists_parts.iterdir():
            p_str = p.as_posix()
            if p_str.startswith(text):
                completions.append(p_str)
    return completions[state]

# we want to treat '/' as part of a word, so override the delimiters
readline.set_completer_delims(' \t\n;')
readline.parse_and_bind("tab: complete")
readline.set_completer(complete_path)
print(input('tab complete a filename: '))

用于路径完成

import os
import sys 
import readline
import glob

def path_completer(text, state):
    """ 
    This is the tab completer for systems paths.
    Only tested on *nix systems
    """
    line = readline.get_line_buffer().split()

    if '~' in text:
        text = os.path.expanduser('~')

    return [x for x in glob.glob(text+'*')][state]
    
if __name__=="__main__":

    readline.set_completer_delims('\t')
    readline.parse_and_bind("tab: complete")

    readline.set_completer(path_completer)
    ans = input("What file do you want? ")
    print(ans)

请注意，我改进了https://gist.github.com/iamatypeofwalrus/5637895中的代码

在Some Systems™上，需要使用不同的绑定，例如，我没有GNU readline，所以需要使用不同的parse_and_bind文本：

if 'libedit' in readline.__doc__:
    readline.parse_and_bind("bind ^I rl_complete")
else:
    readline.parse_and_bind("tab: complete")