ACCEPTED: PEP 285

[Erik Max Francis]

djw wrote:

> Pardon my ignorance (I've only been working with Python for a short
> while), but I don't understand why an idiom like:
> 
> if x == True:
> 
> would be/should be an error (or warning initially).

Because in Python, the canonical way to test for truth, regardless of
what x might be, is:

	if x:
	    ...

Even with PEP 285, there are more values which qualify as true than just
True.  Explicit testing against one of these true values excludes all
others.

> I see C/C++ code
> like this all the time:
> 
> bool x;
> x = Foo(Bar);
> if (x==true)
> {...

This is C++, not C.  In C++ also, the proper way to write this is:

	if (x)
	    ...

Since the if conditional does an implicit conversion to bool, the
explicit test is unnecessary.  The following is completely legal code,
and evaluates the truth clause:

	int x = 1;
	if (x)
	    ...

In C89, which lacks an explicit Boolean type (although one was added to
C99), the above is also the proper way to test for truth.  Just as in
Python, in C++ (and C99) there are more values considered true than just
`true'.  In C89 there isn't even an explicit Boolean type.

> Of course, this could also be written in the more abbreviated form as
> well. But, why force that on the programmer? I really prefer the more
> explicit  comparison of x with true rather than the if(x) idiom.

Because you're leaving out a whole swatch of values that evaluate to
true in a conditional, they just don't have the explicit value true (of
type bool).

-- 
 Erik Max Francis / max at alcyone.com / http://www.alcyone.com/max/
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