Print python float as single precision float

Question

When printing a floating point variable in Python 3 like this:

str(1318516946165810000000000.123123123)

The output is:

1.31851694616581e+24

Is there a simple way in the standard lib (not Numpy) to print the same thing with only 32 bit float precision? (or more general any precision)

Be aware precision != places, like in Decimal

EDIT

The result should should be a string like str does but with a limited precision for example: 32 bit representation of the above float:

1.31851e+24

You mean you want to truncate the decimal representation of a float so that it doesn't give a false impression of accuracy? — that other guy
– that other guy, Commented Aug 12, 2014 at 20:06
Yes, while still ensuring that the result would represent a valid 32 bit float (or any bit precision, like 24 bit), the goal is a string and not the actual python float. I hopend that there would be another way than to manually parse the string again and ensuring said restricitions — compulsoryRegistrationFTW
– compulsoryRegistrationFTW, Commented Aug 12, 2014 at 20:12
So you want a lossless function that can turn a float into a string and back? Does it have to be human readable? — that other guy
– that other guy, Commented Aug 12, 2014 at 20:17

Luke Woodward · Accepted Answer · 2014-08-12 20:45:16Z

1

I may have misunderstood, but is using format with a suitable precision modifier what you are asking for?

>>> "{0:6g}".format(1.31851694616581e24)
'1.31852e+24'

Change the 6 to control the number of significant figures

answered Aug 12, 2014 at 20:45

Luke Woodward

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3 Comments

compulsoryRegistrationFTW Over a year ago

'g' rounds the number to x significant digits (not bits), does not guarantee a valid representation for a 32-bit float, see docs.python.org/3/library/… for details, what could happen is that the float would have a higher or lower value with 6 digits than would be allowed for a x-bit float, none of the format string modifiers looks for bit length

Luke Woodward Over a year ago

OK, thanks for the clarification, sorry my answer's not a lot of help to you.

compulsoryRegistrationFTW Over a year ago

But it can be used in my use case when no further validation is required and a small loss of precision can be ignored, accepting as 'near enough' because there seems no sensible one-liner in the standard lib

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