在Python 3中运行时动态加载模块

在Python3中，建议采用哪种方式延迟加载文件

我通过从Python 2代码中复制过去的代码来构建此函数

def get_command(self, ctx, cmd_name):
        ns = {}
        fn = os.path.join(cmd_folder, 'cmd_{}.py'.format(cmd_name))

        with open(fn) as f:
            code = compile(f.read(), str(fn), 'exec')
            eval(code, ns, ns)

        return ns['cli']

但我不确定这是不是正确的方法。它使用

compile

和

eval

编辑

像这样使用

import

后：

def get_command(self, ctx, cmd_name):
    cmd_mod = import_module('{}.cmd_{}'.format(cmd_folder, cmd_name))

结果是：

  File "aws_iam_cli/cli.py", line 23, in get_command
    cmd_mod = import_module('{}.cmd_{}'.format(cmd_folder, cmd_name))
  File "/Users/salvatoremazzarino/awsiam/venv/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 941, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 953, in _find_and_load_unlocked
ModuleNotFoundError: No module named '/Users/salvatoremazzarino/awsiam/aws_iam_cli/commands'

错误是：

  File "/Users/salvatoremazzarino/awsiam/venv/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 941, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 941, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 953, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'aws_iam_cli'

在命令内部，我有一个模块，我在该模块内部调用：

from aws_iam_cli.provider.role import fetch_roles

---

您可以使用importlib.import_模块在运行时动态加载模块。例如：

from importlib import import_module

# load module
pckg_name = 'commands'  # I assume all your commands are in this pckg
cmd_mod = import_module('{}.cmd_{}'.format(pckg_name, cmd_name))

# run command (I'm assuming the module contains a function with the 'cmd_name')
cmd_mod.cmd_name()

---

我认为这种方法会更干净、更安全，应该与您正在做的工作配合使用。

几乎肯定不会，但您还没有真正描述您的问题。你说的“懒散加载”是什么意思？您将如何使用它？为什么不使用标准的导入？我必须在运行时读取、编译和执行文件，而不是静态导入它们。做这里描述的事情@DanielRoseman那么你会推荐什么？你想用它做什么？答案因“我希望最终用户上传python脚本”和“我希望库用户轻松扩展我的库”而异。您的包（cmd_文件夹）中是否有_init_uuuuuuuuuy.py？是的。我知道了。啊-你的cmd_文件夹是完整路径。我们想要的只是最简单的。e、 g.commands.a_commands不幸的是仍然存在问题。我要更新这个问题，让我们一起来。

from aws_iam_cli.provider.role import fetch_roles

from importlib import import_module

# load module
pckg_name = 'commands'  # I assume all your commands are in this pckg
cmd_mod = import_module('{}.cmd_{}'.format(pckg_name, cmd_name))

# run command (I'm assuming the module contains a function with the 'cmd_name')
cmd_mod.cmd_name()