## Round to significant figures in python

I want to round like this 42949672 -> 42949700, 2147483647 -> 2147480000, 4252017622 -> 4252020000 etc.

I tried to use following , but only works for the first one. How can I make a more general one? thanks

round(42949672, -2)

I assume you want to round to 6 significant figures. If you want to round `int`

s, you can use

def round_sf(number, significant): return round(number, significant - len(str(number))) print(round_sf(4252017622, 6))

Result:

4252020000

**sigfig · PyPI,** Python library for rounding numbers (with expected results) by significant figures/digits; round numbers by decimal places; round numbers by To round an integer to 1 significant figure the basic idea is to convert it to a floating point with 1 digit before the point and round that, then convert it back to its original integer size. To do this we need to know the largest power of 10 less than the integer.

The accepted answer has limitations and does not produce technically correct significant figures in the general case.

numpy.format_float_positional supports the desired behaviour directly. The following fragment returns the float `x`

formatted to 4 significant figures, with scientific notation suppressed.

import numpy as np x=12345.6 np.format_float_positional(x, precision=4, unique=False, fractional=False, trim='k') > 12340.

**How to Round Numbers in Python – Real Python,** You might be wondering, “Can the way I round numbers really have that much of arithmetic is taken care of automatically, and significant digits are preserved. How to round a number to significant figures in Python (8) %g in string formatting will format a float rounded to some number of significant figures. It will sometimes use 'e' scientific notation, so convert the rounded string back to a float then through %s string formatting. >> > '%s' % float ( '%.1g' % 1234 ) '1000' >> > '%s' % float ( '%.1g' % 0.

To round to any digits that you are targeting, you can simply put the digits as a negative number in your round function and then convert it to integer.

digits = 4 num = 2147483647 rounded_num = int(round(num, -digits))

If you are trying to keep 6 significant figures always, that's the pattern that I saw in your question you would want to do this:

def sf_round(num, sig_fig): return int(round(num, -(len(str(num))-sig_fig)))

**[Tutor] Rounding to n significant digits?,** Alan Gauld wrote at 00:05 7/2/2004: > > Is there something (a function?) in Python 2.3.4 that will round a >result > > to n significant digits, or do I To implement the “rounding down” strategy in Python, we can follow the same algorithm we used for both trunctate () and round_up (). First shift the decimal point, then round to an integer, and finally shift the decimal point back. In round_up (), we used math.ceil () to round up to the ceiling of the number after shifting the decimal point.

**15. Floating Point Arithmetic: Issues and Limitations,** format(math.pi, '.12g') # give 12 significant digits '3.14159265359' in the end if you simply round the display of your final results to the number of decimal digits round() is a built-in function in Python. It returns x rounded to n digits from the decimal point. Syntax. Following is the syntax for the round() method − round( x [, n] ) Parameters. x − This is a numeric expression. n − Represents number of digits from decimal point up to which x is to be rounded. Default is 0.

**How to round a number to significant figures in Python ,** How to round a number to significant figures in Python. I need to round a float to be displayed in a UI. E.g, to one significant figure: 1234 -> 1000. 0.12 -> 0.1. Significant Figures in Python This repository contains a couple of functions of dubious merit related to significant figures. sigfig.string () returns a (decimal) string representation of a float with n significant figures. sigfig.round_ () rounds floats (sort of) to n significant figures.

**How to round a number to significant digits in Python,** How to round a number to significant digits in Python. Rounding a number to n significant digits rounds a number and includes only the desired number of This is the sigfig Python package used for rounding numbers (with expected results). >>> round(0.25, 1) 0.2 >>> from sigfig import round >>> round(0.25, decimals=1) 0.3 >>> round(3.14159, sigfigs=2) 3.1 >>> round(3.14159, uncertainty=0.003639) '3.142 ± 0.004' >>> round('3.141592653589793', '0.00000002567', format='Drake') '3.141 592 654 (26)'