On 2017-10-10 16:37, xieyuheng wrote: > > Some callables may not be introspectable in certain implementations of > Python. > > For example, in CPython, some built-in functions defined in C > > provide no metadata about their arguments. > > this is depends on implementation, so I ask for CPython.
There's not really much more to say than what the docs you're quoting say. As far as I'm aware, all callables defined in Python will have a signature, while the default for "built-in" functions (anything written in C) in CPython is for them not to have a signature. This applies to __builtins__ and other modules written in C equally. In __builtins__, most callables have NO signature as of Python 3.6. However, around 3/4 of the *functions* there (i.e. not types) DO have signatures. In particular none of the built-in exceptions have signatures. >>> import inspect >>> no_sig = [] >>> has_sig = [] >>> for name, val in __builtins__.__dict__.items(): ... try: ... tmp = inspect.signature(val) ... except TypeError: ... pass # not callable ... except ValueError: ... no_sig.append(name) ... else: ... has_sig.append(name) ... >>> >>> len(no_sig) 101 >>> len(has_sig) 40 Look at only "functions": >>> [name for name in no_sig if type(getattr(__builtins__, name)) == type(print)] ['__build_class__', '__import__', 'dir', 'getattr', 'iter', 'max', 'min', 'next', 'print', 'round', 'vars'] >>> len([name for name in no_sig if type(getattr(__builtins__, name)) == type(print)]) 11 >>> [name for name in has_sig if type(getattr(__builtins__, name)) == type(print)] ['abs', 'all', 'any', 'ascii', 'bin', 'callable', 'chr', 'compile', 'delattr', 'divmod', 'eval', 'exec', 'format', 'globals', 'hasattr', 'hash', 'hex', 'id', 'input', 'isinstance', 'issubclass', 'len', 'locals', 'oct', 'ord', 'pow', 'repr', 'setattr', 'sorted', 'sum', 'open'] >>> len([name for name in has_sig if type(getattr(__builtins__, name)) == type(print)]) 31 Take out the exceptions and warnings: >>> [name for name in no_sig if name[0] == name[0].lower()] ['__build_class__', '__import__', 'dir', 'getattr', 'iter', 'max', 'min', 'next', 'print', 'round', 'vars', 'bool', 'bytearray', 'bytes', 'classmethod', 'complex', 'dict', 'enumerate', 'filter', 'float', 'frozenset', 'property', 'int', 'list', 'map', 'range', 'reversed', 'set', 'slice', 'staticmethod', 'str', 'super', 'tuple', 'type', 'zip'] >>> len([name for name in no_sig if name[0] == name[0].lower()]) 35 >>> [name for name in has_sig if name[0] == name[0].lower()] ['__loader__', 'abs', 'all', 'any', 'ascii', 'bin', 'callable', 'chr', 'compile', 'delattr', 'divmod', 'eval', 'exec', 'format', 'globals', 'hasattr', 'hash', 'hex', 'id', 'input', 'isinstance', 'issubclass', 'len', 'locals', 'oct', 'ord', 'pow', 'repr', 'setattr', 'sorted', 'sum', 'memoryview', 'object', 'open', 'quit', 'exit', 'copyright', 'credits', 'license', 'help'] >>> len([name for name in has_sig if name[0] == name[0].lower()]) 40 >>> -- Thomas Jollans -- https://mail.python.org/mailman/listinfo/python-list
