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How do I type a floating point infinity literal in python

Posted by: admin November 29, 2017 Leave a comment

Questions:

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?

Answers:

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.

Questions:
Answers:

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.)

Questions:
Answers:

Perhaps you could do something like this

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