CODEWITHSUNDEEP
pythonfloating-pointportabilitynumerical
fmark
fmark

Reputation: 58567

How do I type a floating point infinity literal in python

How do I type a floating point infinity literal in python?

I have heard 

 inf = float('inf')

is non portable. Thus, I have had the following recommended:

 inf = 1e400

Is either of these standard, or portable? What is best practice?

Upvotes: 79

Views: 60313

Answers (4)

barjak
barjak

Reputation: 11270

Starting from Python 3.6, you can use math.inf.

import math
math.inf

Upvotes: 3

John La Rooy
John La Rooy

Reputation: 304147

Perhaps you could do something like this

try:
    inf = float('inf')
except:  # check for a particular exception here?
    inf = 1e30000

Upvotes: 12

kennytm
kennytm

Reputation: 523264

float('inf') is non portable as in not portable back to Python 2.5 when the string output varies between platforms. From 2.6 and onwards float('inf') is guaranteed to work on IEEE-754-compliance platforms (ref: http://www.python.org/dev/peps/pep-0754/).

(And the recommendation seems to be in the range 1e30000, not just 1e400.)

Upvotes: 16

mmmmmm
mmmmmm

Reputation: 32661

In python 2.6 it is portable if the CPU supports it

The float() function will now turn the string nan into an IEEE 754 Not A Number value, and +inf and -inf into positive or negative infinity. This works on any platform with IEEE 754 semantics.

Upvotes: 63

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