David Eppstein eppstein at ics.uci.edu
Wed Apr 3 21:11:54 EST 2002

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In article <3CABB156.1010401 at nospam.attbi.com>,
 djw <dwelch91 at nospam.attbi.com> 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 it will give the wrong result when x is a list, or other type of 
object that is not a bool but can be used as a truth value.

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

C/C++ forces its variables to have declared types, so you can be sure 
that x is a bool -- if it is not true, it must be false.
In Python, you have no guarantees about the type of x, and should be 
prepared to handle any type of value that might make sense in the 
context.

-- 
David Eppstein       UC Irvine Dept. of Information & Computer Science
eppstein at ics.uci.edu http://www.ics.uci.edu/~eppstein/

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