importlib.reload does not "just work". https://docs.python.org/3/library/importlib.html#importlib.reload https://docs.python.org/3/library/importlib.html#import

importlib.reload does not "just work". https://docs.python.org/3/library/importlib.html#importlib.reload https://docs.python.org/3/library/importlib.html#importlib.r... documents what is done and not done. > Doesn't "isinstance" break if you redefine the class? With importlib.reload, yes. You might be interested in IPython's autoreload implementation, which does not break isinstance: https://github.com/ipython/ipython/blob/f8c9ea7db42d9830f16318a4ceca0ac1c3688697/IPython/extensions/autoreload.py#L253-L417 https://github.com/ipython/ipython/blob/f8c9ea7db42d9830f163... However, you could still end up with semi-broken instances, for instance if you update class A: pass to class A: def __init__(self): self.attr = "something" def __str__(self): return self.attr > By the way, you may want to use `import traceback; traceback.print_exc()` to log exceptions. I'm not sure how that plays with python's `logger` class though. PSL logging has builtin integration with exception tracebacks. See Logger.exception [1] or the exc_info keyword param to Logger.debug/info/warning/error/critical/log [2]. [1] https://docs.python.org/3/library/logging.html#logging.Logger.exception https://docs.python.org/3/library/logging.html#logging.Logge... [2] https://docs.python.org/3/library/logging.html#logging.Logger.debug https://docs.python.org/3/library/logging.html#logging.Logge...