How can I limit decimal numbers with a variable with python?

Question

I have a variable called "P", and I want to limit the decimal numbers of a float. The input consists of three lines. The first two lines contain the integer values "a" and "b", respectively. The third line contains the integer p that defines the desired precision. 0<a,b,P≤100 is guaranteed. I want to display the message: "The result of a by b is X.", replacing X with the value of dividing a / b, given to P decimal places.

Ex:

input(a) = 10
input(b) = 5
input(p) = 3
expected result: "2.000"

Ex:

input(a) = 9
input(b) = 3
input(p) = 1
expected result: "3.0"

My code: a = 10, b = 5, p = 2

a = float(input())
b = float(input())
P = int(input())
y = round(a / b, P)
print(f'{a} / {b} = {y}.')

output = 10 / 5 = 2.0.
expected output = 10 / 5 = 2.00.

round is not working well, ex: if P is "2", round just return one decimal number. — Thiago Calegário, Jul 30 '21 at 23:11
What? Please **be specific**. Give an actual example, code we can copy and paste, and provide the output versus the output you were *expecting* — juanpa.arrivillaga, Jul 30 '21 at 23:14
Does this answer your question? [Limiting floats to two decimal points](https://stackoverflow.com/questions/455612/limiting-floats-to-two-decimal-points) — sahasrara62, Jul 30 '21 at 23:43

Marco Bonelli · Accepted Answer · 2021-07-30T23:22:34.687

The round() function does what it's supposed to. The problem is how you want to represent the number. If you always want two decimal digits, even if the number has less significant decimal digits (e.g. you want 1.50 printed instead of 1.5) then you'll have to format the number accordingly when printing:

print(f'{a} / {b} = {y:.{P}f}.')

Here .{P}f is a format specifier for printing a floating point number with exactly P decimal digits, no matter how many significant decimal digits it might have. For more info see the doc on format string syntax.

In fact, if you only need to print such number, your code could be simplified to avoid using round() entirely:

a = float(input())
b = float(input())
P = int(input())
print(f'{a} / {b} = {y:.{P}f}.')

score 0 · Answer 2 · answered Jul 30 '21 at 23:21

0

Modify the result display:

print(f'O resultado de {a} por {b} é {y:.{P}f}.')
                                       ^^^^^^

10
5
2
O resultado de 10.0 por 5.0 é 2.000.

answered Jul 30 '21 at 23:21

Corralien

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How can I limit decimal numbers with a variable with python?

2 Answers2