How to Retrieve an Object by its ID in Python?

Retrieving an Object by its ID in Python

Identifying an object by its unique ID is a crucial task in various programming scenarios. In Python, the id() function can be used to obtain an object's ID. However, the question arises: How can we retrieve the original object given only its ID?

Finding an Object by its ID

If the object is still in memory, it can be retrieved using the ctypes module:

import ctypes

# Get the ID of an object
a = "Hello World"
obj_id = id(a)

# Cast the ID to a Python object
obj = ctypes.cast(obj_id, ctypes.py_object).value

# Print the object's value
print(obj)  # Output: Hello World

Cautionary Notes

While this technique allows you to find an object by its ID, it is important to exercise caution. If the object has been deleted or modified, attempting to retrieve it using this method can lead to undefined behavior and unexpected results. Therefore, it is advisable to ensure that the object still exists before attempting to retrieve it by its ID.

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