().is_integer() not working

Question

Whats wrong with this code:

n = 10
((n/3)).is_integer()

I do not understand why I cannot set n = any number and check if it is an integer or not.

Thanks for your help!

python 2.7.4

error:

Traceback (most recent call last):
  File "/home/userh/Arbeitsfläche/übung.py", line 2, in <module>
    print ((n/3)).is_integer()
AttributeError: 'int' object has no attribute 'is_integer'

Traceback (most recent call last): File "/home/userh/Arbeitsfläche/übung.py", line 2, in print ((n/3)).is_integer() AttributeError: 'int' object has no attribute 'is_integer' — aaaa, Jun 18 '13 at 13:35
Where did you get that is_integer() is a function? Try isinstance(n, int) — Max, Jun 18 '13 at 13:37
@Max probably from http://docs.python.org/2/library/stdtypes.html#float.is_integer — user247702, Jun 18 '13 at 13:38
@Max thank you very much! I assume isinstance works for various things? — aaaa, Jun 18 '13 at 13:41
Reverted your "thanks" edit; please use upvotes to express gratitude instead. — tripleee, Jun 18 '13 at 14:25
@Max is `isinstance(n, int)` better than `n.is_integer()` for some reason? Please clarify why you are suggesting this, thanks — Nathan majicvr.com, Jun 21 '18 at 17:37
@frank Well, other than you've resurrected a 6 year old issue, because not all objects have an is_integer function. ints don't! — Max, Jun 21 '18 at 19:51

Sebastian Ärleryd · Answer 1 · 2013-06-18T13:48:48.687

The reason you get this error is because you divide the integer 10 by 3 using integer division, getting the integral number 3 in the form of an int instance as a result. You then try to call the method is_integer() on that result but that method is in the float class and not in the int class, just as the error message says.

A quick fix would be to change your code and divide by 3.0 instead of 3 which would result in floating point division and give you a float instance on which you can call the is_integer() method like you are trying to. Do this:

n = 10
((n/3.0)).is_integer()

score 6 · Answer 2 · answered Jun 18 '13 at 13:39

6

You are using Python 2.7. Unless you use from __future__ import division, dividing two integers will return you and integer. is_integer exists only in float, hence your error.

answered Jun 18 '13 at 13:39

Morwenn

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score 4 · Answer 3 · answered Jun 18 '13 at 13:53

the other answers say this but aren't very clear (imho).

in python 2, the / sign means "integer division" when the arguments are integers. that gives you just the integer part of the result:

>>> 10/3
3

which means that in (10/3).is_integer() you are calling is_integer() on 3, which is an integer. and that doesn't work:

>>> (3.0).is_integer()
True
>>> (3).is_integer()
AttributeError: 'int' object has no attribute 'is_integer'

what you probably want is to change one of the numbers to a float:

>>> (10/3.0).is_integer()
False

this is fixed in python 3, by the way (which is the future, and a nicer language in many small ways).

@glglgl sorry, but no, i strongly don't agree. a language is a user interface. if it confuses many users it's bad. — andrew cooke, Jun 18 '13 at 14:50

score -1 · Answer 4 · answered Jul 11 '17 at 06:51

-1

You can use isdigit, this is a good function provided by Python itself

You can refer documentation here https://docs.python.org/2/library/stdtypes.html#str.isdigit

    if token.isdigit():
        return int(token)

answered Jul 11 '17 at 06:51

Ravikiran Reddy Kotapati

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This answer only works if one is trying to determine if a string is an integer, so it doesn't appear to answer the question. – Moot Apr 04 '18 at 17:24

Ohlin · Answer 5 · 2013-06-18T13:40:51.257

-2

...

When I wrote this answer there was no information about language.

But in python2 you can use the following to check if it's an integer or not

isinstance( <var>, ( int, long ) )

edited Jun 18 '13 at 13:40

answered Jun 18 '13 at 13:32

Ohlin

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of course, but why do I get this error with is_integer: AttributeError: 'int' object has no attribute 'is_integer' – aaaa Jun 18 '13 at 13:34
1

well, there is no such function for an int object...the error message says it. – Ohlin Jun 18 '13 at 13:36
1

Dv: in Python 2.7, / is integer division if applied to two integers. – Max Jun 18 '13 at 13:37

().is_integer() not working

5 Answers5