On Tue, 7 May 2019 at 06:42, Christopher Barker <python...@gmail.com> wrote:
>
> Oddly, it seems everyone in this thread thinks it would be "Better" to have a
> bunch of constructors, ratehr than the overloading, of only we didn't have
> backward compatibility to worry about.
>
> I disagree -- these efficiencies are what I LIKE about python:
>
> int() tries to turn whatever you pass into into an integer -- a float, a
> string, whatever. Do people really think that it would be better if we all
> had to write:
>
> int.parse("123")
>
> Rather than just int("123") ?
It depends whether you want to have an exception if the wrong type of
input is encountered. The alternative to x=int.parse(s) might instead
be
if not isinstance(s, str):
raise TypeError('need a string')
x = int(s)
One of the things I like about Python compared to e.g. C is that it
often tells me when something is going wrong in some code rather than
silently doing the wrong thing.
The int function accepts all kinds of things e.g.
>>> int('๒')
2
However in my own code if that character ever got passed to int then
it would definitely indicate either a bug in the code or data
corruption so I'd rather have an exception.
Admittedly the non-ASCII unicode digit example is not one that has
actually caused me a problem but what I have had a problem with is
floats. Given that a user of my code can pass in a float in place of a
string the fact that int(1.5) gives 1 can lead to bugs or confusion.
For precisely these reasons there is the __index__ method to get
around this for the situations where you want to convert a non-int
integer type to int (without accepting strings or floats). There is
math.trunc for the situation where you are not parsing strings and
actually do want to accept non-integer numbers and truncate them.
There is no function to parse a decimal integer string without also
accepting floats though.
--
Oscar
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