limited float decimal point without rounding the number

Question

I want convert a number to a float number with 3 decimal point but I want it without rounding. For example:

a = 12.341661
print("%.3f" % a)

This code return this number:

12.342

but I need to original number,I need this:

12.341

I write a code that receive a number form user and convert it to a float number. I have no idea that what is the number entered with user.

You could use string manipulation instead of treating it as a number. — Praveen S, Oct 25 '18 at 20:36
I search stack over flow but could not find my answer. I found just about How to truncating but my Q is How truncating without rounding. — Mehran sanea, Oct 25 '18 at 20:45

joanis · Accepted Answer · 2018-10-26T21:41:01.850

6

My first thought was to change print("%.3f" % a) to print("%.3f" % (a-0.0005)) but it does not quite work: while it outputs what you want for a=12.341661, if a=12.341 it outputs 12.340, which is obviously not right.

Instead, I suggest doing the flooring explicitly using int():

a = 12.341661
b = int(a*1000)/1000.
print(b)

This outputs what you want:

12.341

To get 3 decimals out even if the input has fewer, you can format the output:

a = 3.1
b = int(a*1000)/1000.
print("%.3f" % b)

Outputs:

3.100

edited Oct 26 '18 at 21:41

answered Oct 25 '18 at 20:47

joanis

10,635
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it is good but if user enter 1.1 the code return 1.1 too. but I want 3 decimal means 1.100 – Mehran sanea Oct 25 '18 at 20:57
Just updated my answer to always output 3 decimals. – joanis Oct 26 '18 at 21:41

bilbo_strikes_back · Answer 2 · 2018-10-25T20:46:08.490

0

try str and slicing

a = 12.341661
b = str(int(a))
c = str(a - int(a))[1:5]
d = b + c
print(d)

edited Oct 25 '18 at 20:46

answered Oct 25 '18 at 20:35

bilbo_strikes_back

591
3
10

I have no idea that what is the number entered by user. maybe the number with 10 digit entered. For example: 12023.1288767 – Mehran sanea Oct 25 '18 at 20:38
I edited my post to show you how you can get the number before the decimal and the 3 digits after the decimal – bilbo_strikes_back Oct 25 '18 at 20:46
Doesn't work for negative numbers. – Mark Ransom Oct 25 '18 at 21:01
My inputs are all positive. I think it,s best answer to my Q. – Mehran sanea Oct 25 '18 at 21:05

limited float decimal point without rounding the number

2 Answers2

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