Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!news.albasani.net!rt.uk.eu.org!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
To: python-list@python.org
From: Ben Finney <ben@benfinney.id.au>
Subject: Re: how to check if a value is a floating point or not
Date: Thu, 19 Jun 2014 17:19:44 +1000
References: <d5ca21d7-23e6-4240-83d8-262d0f877f7e@googlegroups.com> <52ba65d1-a5dc-47b5-bccd-e05b24ae3e1f@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.4 (gnu/linux)
Cancel-Lock: sha1:tIZj9FhKCOuaNQZyTqOoVjpWbsI=
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.11132.1403162399.18130.python-list@python.org>
Lines: 47
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:73398

Nicholas Cannon <nicholascannon1@gmail.com> writes:

> #checks if the user input is an integer value
> def checkint(a):
> 	if a.isnumeric():
> 		return True
> 	else:
> 		if a.isalpha():
> 			return False
> 		else:
> 			return True

What code will be using this function? Why would that not be better
replaced with a ‘try … except’ construction?

That is, don't do this (Look Before You Leap)::

    foo = get_a_string()
    if checkint(foo):
        bar = int(foo)
    else:
        bar = None

Instead, do this (Easier to Ask Forgiveness than Permission)::

    foo = get_a_string()
    try:
        bar = int(foo)
    except ValueError:
        bar = None

If you need to create an integer based on a string, just do it, and
handle the exception (if any) at an appropriate level.

> There is one annoying error doing it this way and that is if you enter
> 12.ab or ab.12 it will say that it is okay. Still working on this so
> this should get sorted out soon.

You are re-inventing a wheel (the ‘int’ callable) which already does all
of that properly. Make use of it, and your frustration will be reduced.

-- 
 \     “It is far better to grasp the universe as it really is than to |
  `\    persist in delusion, however satisfying and reassuring.” —Carl |
_o__)                                                            Sagan |
Ben Finney