[python] Reimport a module in python while interactive

I know it can be done, but I never remember how.

How can you reimport a module in python? The scenario is as follows: I import a module interactively and tinker with it, but then I face an error. I fix the error in the .py file and then I want to reimport the fixed module without quitting python. How can I do it ?

In python 3, reload is no longer a built in function.

If you are using python 3.4+ you should use reload from the importlib library instead:

import importlib
importlib.reload(some_module)

If you are using python 3.2 or 3.3 you should:

import imp  
imp.reload(module)  

instead. See http://docs.python.org/3.0/library/imp.html#imp.reload

If you are using ipython, definitely consider using the autoreload extension:

%load_ext autoreload
%autoreload 2

Although the provided answers do work for a specific module, they won't reload submodules, as noted in This answer:

If a module imports objects from another module using from ... import ..., calling reload() for the other module does not redefine the objects imported from it — one way around this is to re-execute the from statement, another is to use import and qualified names (module.*name*) instead.

However, if using the __all__ variable to define the public API, it is possible to automatically reload all publicly available modules:

# Python >= 3.5
import importlib
import types


def walk_reload(module: types.ModuleType) -> None:
    if hasattr(module, "__all__"):
        for submodule_name in module.__all__:
            walk_reload(getattr(module, submodule_name))
    importlib.reload(module)


walk_reload(my_module)

The caveats noted in the previous answer are still valid though. Notably, modifying a submodule that is not part of the public API as described by the __all__ variable won't be affected by a reload using this function. Similarly, removing an element of a submodule won't be reflected by a reload.

Actually, in Python 3 the module imp is marked as DEPRECATED. Well, at least that's true for 3.4.

Instead the reload function from the importlib module should be used:

https://docs.python.org/3/library/importlib.html#importlib.reload

But be aware that this library had some API-changes with the last two minor versions.

Another small point: If you used the import some_module as sm syntax, then you have to re-load the module with its aliased name (sm in this example):

>>> import some_module as sm
...
>>> import importlib
>>> importlib.reload(some_module) # raises "NameError: name 'some_module' is not defined"
>>> importlib.reload(sm) # works

If you want to import a specific function or class from a module, you can do this:

import importlib
import sys
importlib.reload(sys.modules['my_module'])
from my_module import my_function