Round float to x decimals?
Use the built-in function round()
:
In [23]: round(66.66666666666,4)
Out[23]: 66.6667
In [24]: round(1.29578293,6)
Out[24]: 1.295783
help on round()
:
round(number[, ndigits]) -> floating point number
Round a number to a given precision in decimal digits (default 0
digits). This always returns a floating point number. Precision may
be negative.
How to round float numbers in javascript?
Number((6.688689).toFixed(1)); // 6.7
Rounding a double value to x number of decimal places in swift
You can use Swift's round
function to accomplish this.
To round a Double
with 3 digits precision, first multiply it by 1000, round it and divide the rounded result by 1000:
let x = 1.23556789
let y = Double(round(1000 * x) / 1000)
print(y) /// 1.236
Unlike any kind of printf(...)
or String(format: ...)
solutions, the result of this operation is still of type Double
.
EDIT:
Regarding the comments that it sometimes does not work, please read this: What Every Programmer Should Know About Floating-Point Arithmetic
How to round float to certain amount of decimal places Python
You can use the built in round
function:
The second argument in the paranthesis gives the amount of digits to round off
x=input("Enter a decimal number: ")
print(round(float(x),3))
how to convert a float number to 4 decimal places without any rounding?
Based on your expected output for the square root of 3, it seems that you really just want to truncate or extend the square root output to 4 decimal places (rather than round up or down). If that is the case, you could just format to 5 decimal places and slice off the last character in the string (examples below replace your input with hardcoded strings for illustration).
import math
n = '{:.5f}'.format(math.sqrt(float('3')))[:-1]
print(n)
# 1.7320
n = '{:.5f}'.format(math.sqrt(float('4')))[:-1]
print(n)
# 2.0000
How does one round a floating point number to a specified number of digits?
If you want this just for display purposes, use the formatting syntax built into println!()
. For example, to print a number rounded to 2 decimal places use the {:.2}
format specifier:
fn main() {
let x = 12.34567;
println!("{:.2}", x);
}
If you want to put the rounded number in a string, use the format!()
macro.
If you want to round a number and get the result back as another number, then multiply the number by the given power of 10, call round
, and divide by the same power, e.g. to round to 2 decimal places, use 102 = 100.
fn main() {
let x = 12.34567_f64;
let y = (x * 100.0).round() / 100.0;
println!("{:.5} {:.5}", x, y);
}
playground
This prints 12.34567 12.35000
.
If the number of decimal places isn't known at compile time, one could use powi
to efficiently compute the relevant power.
Note that this will breakdown for very large numbers; specifically, numbers larger than std::f64::MAX / power
(where power
is the power of ten, e.g. 100 in the example above) will become infinity in the multiplication, and remain infinity after. However, f64
cannot represent any fractional places for numbers larger than 253 (i.e. they're always integers), so one can special case such large numbers to just return themselves.
How to round to 2 decimals with Python?
You can use the round
function, which takes as its first argument the number and the second argument is the precision after the decimal point.
In your case, it would be:
answer = str(round(answer, 2))
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