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Add the 'bool' type and its values 'False' and 'True', as described in

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PEP 285.  Everything described in the PEP is here, and there is even
some documentation.  I had to fix 12 unit tests; all but one of these
were printing Boolean outcomes that changed from 0/1 to False/True.
(The exception is test_unicode.py, which did a type(x) == type(y)
style comparison.  I could've fixed that with a single line using
issubtype(x, type(y)), but instead chose to be explicit about those
places where a bool is expected.

Still to do: perhaps more documentation; change standard library
modules to return False/True from predicates.
This commit is contained in:
Guido van Rossum 2002-04-03 22:41:51 +00:00
parent e9c0358bf4
commit 77f6a65eb0
29 changed files with 489 additions and 378 deletions
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20
Doc/ref/ref3.tex
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@ -162,7 +162,7 @@ complex numbers:
These represent elements from the mathematical set of whole numbers.
\obindex{integer}
There are two types of integers:
There are three types of integers:
\begin{description}
@ -187,6 +187,17 @@ represented in a variant of 2's complement which gives the illusion of
an infinite string of sign bits extending to the left.
\obindex{long integer}
\item[Booleans]
These represent the truth values False and True. The two objects
representing the values False and True are the only Boolean objects.
The Boolean type is a subtype of plain integers, and Boolean values
behave like the values 0 and 1, respectively, in almost all contexts,
the exception being that when converted to a string, the strings
\code{"False"} or \code{"True"} are returned, respectively.
\obindex{Boolean}
\ttindex{False}
\ttindex{True}
\end{description} % Integers
The rules for integer representation are intended to give the most
@ -222,6 +233,7 @@ and \code{z.imag}.
\end{description} % Numbers
\item[Sequences]
These represent finite ordered sets indexed by non-negative numbers.
The built-in function \function{len()}\bifuncindex{len} returns the
@ -1074,8 +1086,10 @@ wrong hash bucket).
\end{methoddesc}
\begin{methoddesc}[object]{__nonzero__}{self}
Called to implement truth value testing; should return \code{0} or
\code{1}. When this method is not defined, \method{__len__()} is
Called to implement truth value testing, and the built-in operation
\code{bool()}; should return \code{False} or \code{True}, or their
integer equivalents \code{0} or \code{1}.
When this method is not defined, \method{__len__()} is
called, if it is defined (see below). If a class defines neither
\method{__len__()} nor \method{__nonzero__()}, all its instances are
considered true.