How do I unload (reload) a Python module?

Question

I have a long-running Python server and would like to be able to upgrade a service without restarting the server. What\'s the best way do do this?

if foo.py          


        

Answer 1

Removing modules from sys.modules requires 'None' types to be deleted as well.

Method 1:

import sys
import json  ##  your module

for mod in [ m for m in sys.modules if m.lstrip('_').startswith('json') or sys.modules[m] == None ]: del sys.modules[mod]

print( json.dumps( [1] ) )  ##  test if functionality has been removed

Method 2, using bookkeeping entries, to remove all dependencies:

import sys

before_import = [mod for mod in sys.modules]
import json  ##  your module
after_import = [mod for mod in sys.modules if mod not in before_import]

for mod in [m for m in sys.modules if m in after_import or sys.modules[m] == None]: del sys.modules[mod]

print( json.dumps( [2] ) )  ##  test if functionality has been removed

Optional, just to be certain all entries are out, if you so choose:

import gc
gc.collect()