How do I reload a module after changing it?

Question

Python Console with Python 3.4.2

I defined a function in a module which runs correctly in Python Console in PyCharm Community Edition 4.5.4:
ReloadTest.py:

def reloadtest(x):
    print("Version A: {}".format(x))

Python Console:

Python 3.4.2 (v3.4.2:ab2c023a9432, Oct  6 2014, 22:15:05) [MSC v.1600 32 bit (Intel)] on win32
>>> from ReloadTest import reloadtest
>>> reloadtest(1)
Version A: 1   

After I modified the function to "Version B", PyCharm can't find the change, and importlib.reload(ReloadTest) gives me error.
I must reload the Python Console or restart PyCharm every time I modify a module. What did I do wrong? What is the best way to handle this?

ReloadTest.py:

def reloadtest(x):
    print("Version B: {}".format(x))

Python Console:

>>> reloadtest(1)
Version A: 1
>>> from ReloadTest import reloadtest
>>> reloadtest(1)
Version A: 1
>>> import importlib
>>> importlib.reload(ReloadTest)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
NameError: name 'ReloadTest' is not defined
>>> from ReloadTest import reloadtest
>>> reloadtest(1)
Version A: 1
>>> import ReloadTest
>>> reloadtest(1)
Version A: 1

Solution 1

Get it to work!
Instead of from Module import function, I should import the whole module import Module, then call the function by Module.function(). This is because

from ReloadTest import reloadtest

and

importlib.reload(ReloadTest)

can't go together.

>>> import ReloadTest
>>> ReloadTest.reloadtest(1)
Version A: 1

After making changes:

>>> importlib.reload(ReloadTest)
<module 'ReloadTest' from 'C:\\...\\ReloadTest.py'>
>>> ReloadTest.reloadtest(2)
Version B: 2

Solution 2

I took me some time to understand the previous answer... And also, that answer is not very practical if the chuck of code you need to run is in the middle of a script that you do not feel like modifying for running it once.

You can simply do:

import importlib
importlib.reload(my_module)
from my_module import my_function

Then, you can run your code with the updated version of the function.

Works with PyCharm Community Edition 2016.3.2

Edit w.r.t. first comment: This only works if you first imported the module itself (otherwise you get an error as said in the first comment).

import my_module
from my_module import my_function
# Now calls a first version of the function
# Then you change the function
import importlib
importlib.reload(my_module)
from my_module import my_function
# Now calls the new version of the function

Solution 3

You can instruct Pycharm to automatically reload modules upon changing by adding the following lines to settings->Build,Excecution,Deployment->Console->Python Console in the Starting Script:

%load_ext autoreload
%autoreload 2

Update: This function requires IPython (pip install ipython) as described here: Reloading submodules in IPython

Solution 4

Since this question asked specifically about PyCharm, please check out the answer on the PyCharm Support site. This answer is almost identical to @wokbot's, the distinction is that PyCharm removes the need to import importlib. It also uses the from ... import ... trick after import ... to make typing easier if you plan to use reloadtest frequently.

In[2]: import ReloadTest
In[3]: from ReloadTest import reloadtest
In[4]: reloadtest(1)
Out[4]: Version A: 1

...make changes

In[5]: reload(ReloadTest)
Out[5]: <module 'ReloadTest' from 'C:\\...\\ReloadTest.py'>
In[6]: from ReloadTest import reloadtest
In[7] reloadtest(2)
Out[7]Version B: 2

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