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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Thu, 19 Jun 2014 01:37:50 -0600
Subject: Re: how to check if a value is a floating point or not
To: Python <python-list@python.org>
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On Thu, Jun 19, 2014 at 1:23 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> On Thu, Jun 19, 2014 at 12:48 AM, Nicholas Cannon
> <nicholascannon1@gmail.com> wrote:
>> On Thursday, June 19, 2014 1:53:31 PM UTC+8, Nicholas Cannon wrote:
>>> I am making a calculator and i need it to support floating point values=
 but i am using the function isnumeric to check if the user has entered an =
int value. I need the same for floating point types so i could implement an=
 or in the if statement that checks the values the user has entered and all=
ow it to check and use floating points. If you need the source code i am ha=
ppy to give it to you. Thank you for your help
>>
>> I am using python 2.7.7 and i have come up with away but there is still =
possible errors for this. What i did was i this
>>
>> #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
>>
>> The parameter a is the users input by the raw_input function. I first te=
st if it is normal int with the isnumeric function. Unfortunately this func=
tion picks up the decimal as false. This means if the user inputs a float i=
t has to be false. I then test if this input has any alphabetical character=
s if it does not the user could have only entered  something like 12.5 oppo=
se to abc.d.
>
> unicode.isalpha does not test if the input has *any* alphabetic
> characters.  It tests if the input is *only* alphabetic characters.
> u'12.5'.isalpha() does return False.  u'abc.d'.isalpha() *also*
> returns False, because the decimal point is not alphabetic.

Incidentally, unicode.isnumeric is probably not what you want either.
According to the docs, it returns "True if there are only numeric
characters in S, False otherwise. Numeric characters include digit
characters, and all characters that have the Unicode numeric value
property, e.g. U+2155, VULGAR FRACTION ONE FIFTH."  So that includes
strings like u'123=E2=85=95=E2=85=93=E2=85=A7=D9=A4', which is clearly not =
an integer.  You'd
likely do better with unicode.isdigit, and even then you'd be allowing
for mixed scripts.