How can I represent an infinite number in Python?
PythonInfiniteInfinityPython Problem Overview
How can I represent an infinite number in python? No matter which number you enter in the program, no number should be greater than this representation of infinity.
Python Solutions
Solution 1 - Python
In Python, you can do:
test = float("inf")
In Python 3.5, you can do:
import math
test = math.inf
And then:
test > 1
test > 10000
test > x
Will always be true. Unless of course, as pointed out, x is also infinity or "nan" ("not a number").
Additionally (Python 2.x ONLY), in a comparison to Ellipsis, float(inf) is lesser, e.g:
float('inf') < Ellipsis
would return true.
Solution 2 - Python
Since Python 3.5 you can use math.inf:
>>> import math
>>> math.inf
inf
Solution 3 - Python
No one seems to have mentioned about the negative infinity explicitly, so I think I should add it.
For negative infinity:
-math.inf
For positive infinity (just for the sake of completeness):
math.inf
Solution 4 - Python
I don't know exactly what you are doing, but float("inf") gives you a float Infinity, which is greater than any other number.
Solution 5 - Python
There is an infinity in the NumPy library: from numpy import inf. To get negative infinity one can simply write -inf.
Solution 6 - Python
Another, less convenient, way to do it is to use Decimal class:
from decimal import Decimal
pos_inf = Decimal('Infinity')
neg_inf = Decimal('-Infinity')
Solution 7 - Python
In python2.x there was a dirty hack that served this purpose (NEVER use it unless absolutely necessary):
None < any integer < any string
Thus the check i < '' holds True for any integer i.
It has been reasonably deprecated in python3. Now such comparisons end up with
TypeError: unorderable types: str() < int()
Solution 8 - Python
Also if you use SymPy you can use sympy.oo
>>> from sympy import oo
>>> oo + 1
oo
>>> oo - oo
nan
etc.
Solution 9 - Python
For Positive Infinity
pos_inf_val = float("infinity")
For Negative Infinity
neg_inf_val = float("-infinity")
Solution 10 - Python
Representing ∞ in python
float("inf") or float("INF") or float("Inf") or float("inF") or float("infinity") or float("Infinity") creates a float object holding ∞
You can also represent -∞ in python
float("-inf") or float("-INF") or float("-Inf") or float("-infinity") creates a float object holding -∞
You can perform arithmetic operations:
infinity = float("inf")
ninfinity = float("-inf")
nan = float("nan")
print(infinity*infinity)#inf
print(ninfinity+infinity)#not a number
print(1/-infinity)#is -0.0
print(nan*nan)# is not a number
print(1/infinity) # is 0.0 since 1/∞ is 0
Output:
$ python3 floating.py
inf
nan
-0.0
nan
0.0
Solution 11 - Python
In Summary, there is two kinds definition for Infinity.
For Positive Infinity
posVal1 = math.inf
posVal2 = float("inf")
For Negative Infinity
negVal1 = -math.inf
negVal2 = float("-inf")