On 26 February 2015 00:11:24 GMT+00:00, Ben Finney <ben+pyt...@benfinney.id.au> wrote: >> Yes, but my point is: You shouldn't need to rebind those names (or >> have names "true" and "false" for 0 and 1). > >That's not what you asked, though. You asked “When would 0 mean true >and >1 mean false?” My answer: in all Unix shell contexts. > >> Instead, use "success" and "failure". > >You'd better borrow the time machine and tell the creators of Unix. The >meme is already established for decades now.
0 = success and non-zero = failure is the meme established, rather than 0 = true, non-zero = false. It's not just used by UNIX, and is not necessarily defined by the shell either (bash was mentioned elsewhere in the thread). There is probably a system that pre-dates UNIX that I uses/used this too, but I don't know. C stdlib defines EXIT_SUCCESS = 0, yet C99 stdbool.h defines false = 0. That shells handle 0 as true and non-zero as false probably stems from this (or similar in older languages). The " true" command is defined to have an exit status of 0, and "false" an exit status of 1. The value is better thought of an error level, where 0 is no error and non-zero is some error. The AmigaOS shell conventionally takes this further with higher values indicating more critical errors, there's even a "failat N" command that means exit the script if the error level is higher than N. None of the above is a good reason to use error *or* success return values in Python--use exceptions!--but may be encountered when running other processes. Simon -- https://mail.python.org/mailman/listinfo/python-list
