Reimport a module in python while interactive
PythonPython Problem Overview
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 ?
Python Solutions
Solution 1 - Python
For Python 3.4+:
import importlib
importlib.reload(nameOfModule)
For Python < 3.4:
reload(my.module)
From the Python docs
> Reload a previously imported module. The argument must be a module object, so it must have been successfully imported before. This is useful if you have edited the module source file using an external editor and want to try out the new version without leaving the Python interpreter.
Don't forget the caveats of using this method:
-
When a module is reloaded, its dictionary (containing the module’s global variables) is retained. Redefinitions of names will override the old definitions, so this is generally not a problem, but if the new version of a module does not define a name that was defined by the old version, the old definition is not removed.
-
If a module imports objects from another module using
from ... import ...
, callingreload()
for the other module does not redefine the objects imported from it — one way around this is to re-execute thefrom
statement, another is to useimport
and qualified names (module.*name*
) instead. -
If a module instantiates instances of a class, reloading the module that defines the class does not affect the method definitions of the instances — they continue to use the old class definition. The same is true for derived classes.
Solution 2 - Python
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
Solution 3 - Python
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.
Solution 4 - Python
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
Solution 5 - Python
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
Solution 6 - Python
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.
Solution 7 - Python
import sys
del sys.modules['module_name']
import module_name