"Don't rebind built-in names*" - it confuses readers

[Chris Angelico]

On Thu, Jun 13, 2013 at 5:40 AM, Mark Janssen <dreamingforward at gmail.com> wrote:
> On Wed, Jun 12, 2013 at 7:24 AM, Grant Edwards <invalid at invalid.invalid> wrote:
>> On 2013-06-11, Mark Janssen <dreamingforward at gmail.com> wrote:
>>>>         list = []
>>>> Reading further, one sees that the function works with two lists, a list of
>>>> file names, unfortunately called 'list',
>>>
>>> That is very good advice in general:  never choose a variable name
>>> that is a keyword.
>>
>> You can't choose a vriable name that is a keyword: the compiler won't
>> allow it.
>>
>> "list" isn't a keyword.
>
> You're right.  I was being sloppy.

We're talking about builtins, and unfortunately there are... well, let
me ask Thespis, from the play of the same name:

Thespis: Oh, then I suppose there are some complaints?
Mercury: Yes, there are some.
Thespis (disturbed): Oh, perhaps there are a good many?
Mercury: There are a good many.
Thespis: Oh, perhaps there are a thundering lot?
Mercury: There are a thundering lot.
Thespis (very much disturbed): Oh.

>>> dir(__builtins__)
['ArithmeticError', 'AssertionError', 'AttributeError',
'BaseException', 'BlockingIOError', 'BrokenPipeError', 'BufferError',
'BytesWarning', 'ChildProcessError', 'ConnectionAbortedError',
'ConnectionError', 'ConnectionRefusedError', 'ConnectionResetError',
'DeprecationWarning', 'EOFError', 'Ellipsis', 'EnvironmentError',
'Exception', 'False', 'FileExistsError', 'FileNotFoundError',
'FloatingPointError', 'FutureWarning', 'GeneratorExit', 'IOError',
'ImportError', 'ImportWarning', 'IndentationError', 'IndexError',
'InterruptedError', 'IsADirectoryError', 'KeyError',
'KeyboardInterrupt', 'LookupError', 'MemoryError', 'NameError',
'None', 'NotADirectoryError', 'NotImplemented', 'NotImplementedError',
'OSError', 'OverflowError', 'PendingDeprecationWarning',
'PermissionError', 'ProcessLookupError', 'ReferenceError',
'ResourceWarning', 'RuntimeError', 'RuntimeWarning', 'StopIteration',
'SyntaxError', 'SyntaxWarning', 'SystemError', 'SystemExit',
'TabError', 'TimeoutError', 'True', 'TypeError', 'UnboundLocalError',
'UnicodeDecodeError', 'UnicodeEncodeError', 'UnicodeError',
'UnicodeTranslateError', 'UnicodeWarning', 'UserWarning',
'ValueError', 'Warning', 'WindowsError', 'ZeroDivisionError', '_',
'__build_class__', '__debug__', '__doc__', '__import__', '__name__',
'__package__', 'abs', 'all', 'any', 'ascii', 'bin', 'bool',
'bytearray', 'bytes', 'callable', 'chr', 'classmethod', 'compile',
'complex', 'copyright', 'credits', 'delattr', 'dict', 'dir', 'divmod',
'enumerate', 'eval', 'exec', 'exit', 'filter', 'float', 'format',
'frozenset', 'getattr', 'globals', 'hasattr', 'hash', 'help', 'hex',
'id', 'input', 'int', 'isinstance', 'issubclass', 'iter', 'len',
'license', 'list', 'locals', 'map', 'max', 'memoryview', 'min',
'next', 'object', 'oct', 'open', 'ord', 'pow', 'print', 'property',
'quit', 'range', 'repr', 'reversed', 'round', 'set', 'setattr',
'slice', 'sorted', 'staticmethod', 'str', 'sum', 'super', 'tuple',
'type', 'vars', 'zip']

I think I can safely say that all the names beginning with an
uppercase letter (exceptions, True/False/None/Ellipsis), and the ones
beginning with underscores, should not be overridden. Well and good.
Still leaves 72 builtins. Obviously overriding len, print, range, etc
would be risky (unless, as mentioned above, you're making a drop-in
replacement), but there are plenty that you'd never notice (eg if you
use "hash" for an encoded password, or "input" for the string the user
typed into an HTML form). I would hope, for instance, that an editor
would not color-highlight 'credits' differently, as it's designed for
interactive work. There are plenty in the grey area - is it safe to
use "sum" as an accumulator or "min" for a unit of time? What about
using "super" to store the amount of retirement money you've put away?
I'd be inclined to avoid this sort any time I'm aware of them, just
because it'll make debugging easier on the day when something goes
wrong.

ChrisA