Call built-in method of object instance, lost self param?

>>> class Foo:
...  f=print
...
>>> Foo.f(2)
2
>>> Foo().f(2)
2
>>> def f(*args): print(*args)
...
>>> class Foo:
...  f=f
...
>>> Foo.f(2)
2
>>> Foo().f(2)
<__main__.Foo object at 0x7b16f5e810> 2

Is there any difference between f and print? Is this a bug?

Is there any difference between f and print?

There is:

>>> f = lambda *args: print(*args)
>>> f.__self__
Traceback (most recent call last):
  File "<python-input-1>", line 1, in <module>
    f.__self__
AttributeError: 'function' object has no attribute '__self__'. Did you mean: '__call__'?
>>> print.__self__
<module 'builtins' (built-in)>

If you take look on the print declaration, it has self argument (bound to it's module):

cpython/Python/bltinmodule.c

Lines 2159 to 2162 in 16dcb57

    
           static PyObject * 
        
           builtin_print_impl(PyObject *module, PyObject * const *args, 
        
                              Py_ssize_t args_length, PyObject *sep, PyObject *end, 
        
                              PyObject *file, int flush)

IIUIC, rules for module functions are like for classmethods, described here: https://docs.python.org/3/reference/datamodel.html#instance-methods

Maybe it should be explained better in https://docs.python.org/3.14/reference/datamodel.html#built-in-functions. BTW, __self__ description here is wrong - at least here we have a documentation issue.

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Call built-in method of object instance, lost self param? #132299

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	static PyObject *
	builtin_print_impl(PyObject module, PyObject const *args,
	Py_ssize_t args_length, PyObject sep, PyObject end,
	PyObject *file, int flush)

Call built-in method of object instance, lost self param? #132299

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skirpichev commented on Apr 9, 2025

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