On Jun 11, 5:14 am, Terry Jan Reedy <tjre...@udel.edu> wrote: > Many long-time posters have advised "Don't rebind built-in names*. > > * Unless you really mean to mask it, or more likely wrap it, such as > wrapping print to modify some aspect of its operation than one cannot do > with its keyword parameters. The point for this post is that such > wrapping modify or extend the basic meaning of the builtin, but do not > abolish it. > > Reasons have been given in various related forms: 'my long experience > tells me its bad', 'you may need the builtin later', 'you may forget > that you rebound the builtin, 'it can lead to subtle bugs, etc. > > Leaving aside the code writer and code operation, I recently discovered > that it is not nice for readers, whether humans or programs. > > For instance, open Lib/idlelib/GrepDialog.py in an editor that colorizes > Python syntax, such as Idle's editor, jump down to the bottom and read > up, and (until it is patched) find > list.append(fn) > with 'list' colored as a builtin. Stop. That looks wrong. List.append > needs two arguments: a list instance and an object to append to the > list. The 'solution' is in a previous line > list = [] > Reading further, one sees that the function works with two lists, a list > of file names, unfortunately called 'list', and a list of > subdirectories, more sensibly call 'subdirs'. I was initially confused > and reading the code still takes a small bit of extra mental energy. > Idle stays confused and will wrongly color the list instance name until > it is changed. Calling the file list 'fnames' or 'filenames' would have > been clearer to both me and Idle. > > -- > Terry Jan Reedy
Pascal introduced the idea of block structure -- introduce a name at one level, override it at a lower level. [Ok ALgol introduced, Pascal popularized]. This has caused more trouble than it has solved. And so languages nowadays tend to 'protect' against this feature. Here is Erlang's 'sticky' feature http://books.google.co.in/books?id=Qr_WuvfTSpEC&pg=PA181&lpg=PA181&dq=erlang+sticky+directory&source=bl&ots=aLZCjwzUFb&sig=DQiiQgzHCt5EtE5H3WY3bCWh4eM&hl=en&sa=X&ei=gYu2UbD6DMOMrQeNh4HYDA&ved=0CEAQ6AEwAw#v=onepage&q=erlang%20sticky%20directory&f=false that prevents a programmer from overriding a builtin module unless he explicitly asks for that. -- http://mail.python.org/mailman/listinfo/python-list
