Re: LBYL vs EAFP

[Ethan Furman]

On 02/04/2013 03:16 PM, Steven D'Aprano wrote:
The eternal conflict between "Look Before You Leap" and "Easier to Ask for
Forgiveness than Permission" (LBYL vs EAFP) continues...
I want to check that a value is a number. Let's say I don't care what sort
of number -- float, int, complex, Fraction, Decimal, something else -- just
that it is a number. Should I:

Look Before I Leap:

     from numbers import Number
     if isinstance(x, Number):
         ...
     else:
         raise TypeError


or Ask Forgiveness:

     x + 0
     ...

As Ian mentioned, both cases are LYBL, unless of course your addition 
was just an example of some mathematical code you have further down.

Personally, I go with EAFP unless I'm trying to present friendlier error 
messages.

~Ethan~
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