PEP 285: Adding a bool type

[Erno Kuusela]

In article <mailman.1017466974.6751.python-list at python.org>, Guido van
Rossum <guido at python.org> writes:

[...]
|     1) Should this PEP be accepted at all.

no.

[...]
| Rationale

|     Most languages eventually grow a Boolean type; even C99 (the new
|     and improved C standard, not yet widely adopted) has one.

i don't agree wit this argument.

|     Many programmers apparently feel the need for a Boolean type; most
|     Python documentation contains a bit of an apology for the absence
|     of a Boolean type.  I've seen lots of modules that defined
|     constants "False=0" and "True=1" (or similar) at the top and used
|     those.  The problem with this is that everybody does it
|     differently.  For example, should you use "FALSE", "false",
|     "False", "F" or even "f"?  And should false be the value zero or
|     None, or perhaps a truth value of a different type that will print
|     as "true" or "false"?  Adding a standard bool type to the language
|     resolves those issues.

clearly you should not use constants, but use 0 and 1. i've
personally not seen any code that uses constants like that.
i'm sure you could find many other questionable practices used
by many modules. i don't agree with this argument either.

|     Some external libraries (like databases and RPC packages) need to
|     be able to distinguish between Boolean and integral values, and
|     while it's usually possible to craft a solution, it would be
|     easier if the language offered a standard Boolean type.

this is true, but not very significant.

|     The standard bool type can also serve as a way to force a value to
|     be interpreted as a Boolean, which can be used to normalize
|     Boolean values.  Writing bool(x) is much clearer than "not not x"
|     and much more concise than

|         if x:
|             return 1
|         else:
|             return 0

i say add a bool() builtin that returns 0 or 1, if it makes you
feel better.


|     Here are some arguments derived from teaching Python.
[...]

in my experience, even absolute beginners naturally understand
that 0 means false and 1 means true.

the fact that other objects are interpreted as true or false can be
slightly confusing, but in my opinion this is not enough of a problem
to warrant the addition to language basics.

keep python clean! ;)

  -- erno