I have a variable in Python containing a floating point number (e.g.
num = 24654.123), and I’d like to determine the number’s precision and scale values (in the Oracle sense), so 123.45678 should give me (8,5), 12.76 should give me (4,2), etc.
I was first thinking about using the string representation (via
repr), but those fail for large numbers (although I understand now it’s the limitations of floating point representation that’s the issue here):
>>> num = 1234567890.0987654321 >>> str(num) = 1234567890.1 >>> repr(num) = 1234567890.0987654
Good points below. I should clarify. The number is already a float and is being pushed to a database via cx_Oracle. I’m trying to do the best I can in Python to handle floats that are too large for the corresponding database type short of executing the INSERT and handling Oracle errors (because I want to deal with the numbers a field, not a record, at a time). I guess
map(len, repr(num).split('.')) is the closest I’ll get to the precision and scale of the float?
Getting the number of digits to the left of the decimal point is easy:
The number of digits to the right of the decimal point is trickier, because of the inherent inaccuracy of floating point values. I’ll need a few more minutes to figure that one out.
Edit: Based on that principle, here’s the complete code.
import math def precision_and_scale(x): max_digits = 14 int_part = int(abs(x)) magnitude = 1 if int_part == 0 else int(math.log10(int_part)) + 1 if magnitude >= max_digits: return (magnitude, 0) frac_part = abs(x) - int_part multiplier = 10 ** (max_digits - magnitude) frac_digits = multiplier + int(multiplier * frac_part + 0.5) while frac_digits % 10 == 0: frac_digits /= 10 scale = int(math.log10(frac_digits)) return (magnitude + scale, scale)
Answered By – Mark Ransom
Answer Checked By – Willingham (BugsFixing Volunteer)