Numerical values such as 1.23 and 34.5 are decimal numbers, aren't they? It is not an integer. 1.0 and 34.0 are also decimal numbers, but they may be called integers.
Fractions such as 1/3 are also not integers. A 3/3 fraction can be called an integer.
Here we define an integer like this. "In addition to 1 and 34, numbers with 0 decimal places such as 1.0 and 3.0 and fractions with the same numerator and denominator"
In this article, we'll look at how to determine literals that are fractions and decimals but also integers.
For pure integers and decimals, all you have to do is enter a number in the variable, like this:
a = 123
b = 123.4
print(a)
print(b)
# 123
# 123.4
On the other hand, when it comes to fractions, if you write "1/4" as above, the calculation process will be performed automatically, so it cannot be expressed. So we use Python's standard library fractions.
from fractions import Fraction
f = Fraction(1, 3)
print(f)
# 1/3
Decimal numbers can be determined by using the is_integer () method.
n = 1.23
print(n.is_integer())
# False
m = 1.00
print(m.is_integer())
# True
However, it cannot be used for fractional representation using fractions.
from fractions import Fraction
f = Fraction(1, 3)
print(f.is_integer())
# AttributeError: 'Fraction' object has no attribute 'is_integer'
What if I can't use the is_integer () method for fractions? If you convert the literal defined as a fraction to a decimal (float type), the is_integer () method should work fine.
A literal defined as a fraction is converted to a decimal by dividing it by ~~ 1.0. ~~
Please point out in the comment section
I changed it to be intuitive and easy to understand by the approach of float (hoge).
By inserting this operation, it is possible to judge by the is_integer () method.
from fractions import Fraction
f = Fraction(1, 3)
g = float(f)
x = Fraction(3, 3)
y = float(x)
print(g)
print(y)
# 0.3333333333333333
# 1.0
print(g.is_integer())
print(y.is_integer())
# False
# True
I will also introduce a detour judgment method that I thought at the time when I did not know the existence of is_integer.
** If the number rounded up to the nearest whole number and the number rounded down to the nearest whole number match, it is judged as an integer ** We will approach based on the idea.
For example, for the number 1.1, rounding up to the nearest whole number gives 2. Conversely, it is 1 if it is rounded down to the nearest whole number. This is not an integer because the numbers do not match.
If it is 1.0, it will be the same 1 regardless of whether it is rounded up or down after the decimal point, so if this is an integer, that is the reason.
To round up the decimal point, use the ceil () method of the math library, By using the floor () method of the math library for devaluation, it is possible to make such a determination. The function below is also valid for decimal numbers such as 1.23.
from fractions import Fraction
import math
def isInteger(n):
nx = math.ceil(n)
ny = math.floor(n)
return (nx == ny)
n = Fraction(1, 3)
m = Fraction(3, 3)
print(isInteger(n))
print(isInteger(m))
# False
# True