How do I type a floating point infinity literal in python

How do I type a floating point infinity literal in pytho开发者_StackOverflow中文版n?

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?

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.

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.)

Perhaps you could do something like this

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

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

import math
math.inf