CODEWITHSUNDEEP
pythonpython-3.xvariablesjupyter-notebook
Singh.Navneet
Singh.Navneet

Reputation: 37

Delete all variables/objects from python environment using a function

I am using Jupyter Notebook and want to delete all the variables created after a certain point. I am able to do it using a for-loop looping through dir() and comparing it to the checkpoint that I create at the cell using checkpoint = list(dir()).

My goal is to clear the environment without losing the libraries that I import in the beginning (which is where I create my checkpoint). Anything I want to retain further, I can add to the checkpoint list and delete the rest.

The issue is, I don't want to write the same for-loop again whenever I want to clear the variables. As soon as I wrap that loop in a function, it stops working. There is no error; but there is no effect either.

Loop:

for i in list(dir()):
    if i not in checkpoint:
        exec('del {}'.format(i))

The same loop wrapped in a function:

def clear_variables():
    for i in list(dir()):
        if i not in checkpoint:
            exec('del {}'.format(i))

The loop works. The function doesn't.

Upvotes: 2

Views: 583

Answers (1)

Mad Physicist
Mad Physicist

Reputation: 114330

It sounds like you are trying to update your global dictionary. You can't safely delete values from a dictionary while you're iterating over it, so you can make a copy of the keys first:

def clear_setpoint(keep, globals=globals()):
    keep = set(keep)
    for key in list(globals.keys()):
        if key not in keep:
            del globals[key]

If your only goal is to preserve imported modules, you don't even need to create a checkpoint:

from types import ModuleType, FunctionType

def clear_all(globals=globals()):
    for key in list(globals.keys()):
        value = globals[key]
        if not isinstance(value, (ModuleType, FunctionType, type)) or \
              (isinstance(value, FunctionType, type) and value.__module__ == globals['__name__'] and value.__name__ != 'clear_all'):
            del globals[key]

This version will automatically delete anything that is not a function, module or class. Classes and functions that are in the current module, based on their __module__ attribute, are deleted as well. Other classes and functions are l And of course, you don't want to delete the function itself :)

kely to be imported, so are not deleted. This won't preserve imported constants, like if you do from math import pi. You can combine the two approaches to preserve imports like that.

Upvotes: 2

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