Fix model_input_names singleton issue causing shared state#42051
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yashwantbezawada wants to merge 1 commit intohuggingface:mainfrom
Open
Fix model_input_names singleton issue causing shared state#42051yashwantbezawada wants to merge 1 commit intohuggingface:mainfrom
yashwantbezawada wants to merge 1 commit intohuggingface:mainfrom
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Fixes huggingface#42024 The model_input_names attribute was defined as a class-level list, and when initializing tokenizer instances, they were all pointing to the same list object. This meant modifying model_input_names on one instance would affect all other instances. The issue was in tokenization_utils_base.py line 1417: ```python self.model_input_names = kwargs.pop("model_input_names", self.model_input_names) ``` When no model_input_names is passed in kwargs, it would use the class attribute directly (self.model_input_names), creating a reference to the shared list instead of creating a new list for the instance. Fixed by wrapping it in list() to ensure each instance gets its own copy: ```python self.model_input_names = list(kwargs.pop("model_input_names", self.model_input_names)) ``` This is a standard pattern for handling mutable default values in Python.
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This solution LGTM but cc @ArthurZucker @itazap! |
This was referenced Apr 29, 2026
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What does this PR do?
Fixes #42024
I found this while testing tokenizers - when you modify
model_input_nameson one tokenizer instance, it was affecting all other instances of the same tokenizer class.The problem is that
model_input_namesis defined as a class-level list, and in the__init__method (line 1417), when no custommodel_input_namesis provided, it was just referencing the class attribute directly instead of making a copy.So all instances were sharing the same list object. This is a classic Python gotcha with mutable class attributes.
The fix is simple - wrap it in
list()to create a new list for each instance:Before:
After:
This ensures each tokenizer instance gets its own independent copy of the list. Now modifications to one instance won't affect others.
The reproduction from the issue shows the problem clearly - with the fix, the second tokenizer instance will have the original list values instead of inheriting the modifications from the first instance.