Nicely representing a floating-point number in python
- by dln385
I want to represent a floating-point number as a string rounded to some number of significant digits, and never using the exponential format. Essentially, I want to display any floating-point number and make sure it “looks nice”.
There are several parts to this problem:
I need to be able to specify the
number of significant digits.
The number of significant digits
needs to be variable, which can't be
done with with the string formatting
operator.
I need it to be rounded the way a
person would expect, not something
like 1.999999999999
I've figured out one way of doing this, though it looks like a work-round and it's not quite perfect. (The maximum precision is 15 significant digits.)
>>> def f(number, sigfig):
return ("%.15f" % (round(number, int(-1 * floor(log10(number)) + (sigfig - 1))))).rstrip("0").rstrip(".")
>>> print f(0.1, 1)
0.1
>>> print f(0.0000000000368568, 2)
0.000000000037
>>> print f(756867, 3)
757000
Is there a better way to do this? Why doesn't Python have a built-in function for this?
