How can I read '0.00' as a number in Python while preserving number of significant digits?

Question

How would i turn "0.00" into an int without getting invalid literal for int() with base 10: '0.00' error?

Heres my current code;

a = int('0.00')        # which gives me an error
a = int(float('0.00')) # gives me 0, not the correct value of 0.00

any suggestion would be appreciated!

You said you want "an int", and `a = int(float('0.00'))` gives an int — PrinceOfCreation, Mar 24 '19 at 19:55
What's wrong with the second one? 'int' does not have any decimal places. — , Mar 24 '19 at 19:55
`0.00` is not an int, it's a float. Integers by definition are whole numbers. — Charles Duffy, Mar 24 '19 at 19:55
@stackoverflown, ...and `0.0` is the correct representation. IEEE floating-point, as used by most major programming languages, does not track number of digits of precision. — Charles Duffy, Mar 24 '19 at 19:56
Yes. Well, technically you get numbers that (when converted to a string) show up as 0 (`int`) or 0.0 (`float`). If you want `0.00` exactly, then use a string. — melpomene, Mar 24 '19 at 19:56
i think you have an underlying assumption here that i'd like to challenge. `0.00` is a valid "representation" of the number 0, but it is NOT stored that way, nor does it need to be. — Paritosh Singh, Mar 24 '19 at 19:56
@PrinceOfCreation i get that, the question im doing requires "0.00" to two decimal places.. — stackoverflown, Mar 24 '19 at 19:59
If the question requires 0.00 to 2 dp. surely the original string value is fine. If you want to print it, print the string. If you want to do maths with it, convert it to a float. — PrinceOfCreation, Mar 24 '19 at 20:00
@stackoverflown and the point is, if someone asks for "0.00" to 2 decimal places, they are asking for a "string representation". melpomene hinted at it too. It is very common to use string formatting to display ints upto certain precision (with stuff like `:.2f` precision) — Paritosh Singh, Mar 24 '19 at 20:01
You have to learn to divide the data (`0`) and its representations (`0`, `0.0` , `0.00`, `-0`, ...). — Klaus D., Mar 24 '19 at 20:01

Charles Duffy · Answer 1 · 2019-03-24T20:14:53.120

If you need to track the number of significant digits past the decimal, neither float nor int is the correct way to store your number. Instead, use Decimal:

from decimal import Decimal
a = Decimal('0.00')
print(str(a))

...emits exactly 0.00.

If doing this, you should probably also read the question Significant figures in the decimal module, and honor the accepted answer's advice.

Of course, you can also round to a float or an int, and then reformat to the desired number of places:

a = float('0.00')
print('%.2f' % a)         # for compatibility with ancient Python
print('{:.2f}'.format(a)) # for compatibility with modern Python
print(f"{a:.2f}")         # for compatibility with *very* modern Python

For good form, perhaps suggest using str format instead of old formatting, something like `print('{:.2f}'.format(a))` or f-strings like `print(f"{a:.2f}")` for python 3.6+ — Paritosh Singh, Mar 24 '19 at 20:04

How can I read '0.00' as a number in Python while preserving number of significant digits?

1 Answers1