How to have negative zero always formatted as positive zero in a python string?

Question

I have the following to format a string:

'%.2f' % n

If n is a negative zero (-0, -0.000 etc) the output will be -0.00.

How do I make the output always 0.00 for both negative and positive zero values of n?

(It is fairly straight forward to achieve this but I cannot find what I would call a succinct pythonic way. Ideally there is a string formatting option that I am not aware of.)

[x + (-0) = x](http://en.wikipedia.org/wiki/Signed_zero#Arithmetic) — georg, Jun 13 '12 at 08:32

eumiro · Accepted Answer · 2012-06-13T08:26:04.587

85

Add zero:

>>> a = -0.0
>>> a + 0
0.0

which you can format:

>>> '{0:.3f}'.format(a + 0)
'0.000'

edited Jun 13 '12 at 08:26

answered Jun 13 '12 at 08:18

eumiro

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This actually made me laugh out loud. Wonderful. – Tim Pietzcker Jun 13 '12 at 08:23
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In your example you can change `0.` to `0`. – jamylak Jun 13 '12 at 08:28
Thanks @eumiro this is exactly what I was looking for. – Dan Jun 13 '12 at 15:09
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Amazing. Even though I'm sure someone will read some code using this trick and will think "Why the hell does he add zero to all his floats?!" – LeartS Aug 20 '14 at 10:39

score 6 · Answer 2 · answered Apr 13 '16 at 16:59

6

A very closely related problem is that -0.00001 is also formatted as "-0.00". That can be just as confusing. The answers above will not take care of this (except for user278064's, which needs an anchored regexp).

It's ugly, but this is the best I can do for this case:

import re
re.sub (r"^-(0\.?0*)$", r"\1", "%.2f" % number)

answered Apr 13 '16 at 16:59

Tim Adye

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if round(v * 1000) == 0: v= 0.0 – Tatarize Sep 27 '19 at 14:34
For my example, I guess you mean `v*100`. Maybe a simpler version is: `if round(v,2) == 0: v= 0.0` . The problem is that this changes the value of v after the print, which is not good. So how about: `"%.2f" % (0.0 if round(v,2) == 0 else v)` . – Tim Adye Sep 30 '19 at 10:41

score 2 · Answer 3 · answered Jun 13 '12 at 08:24

The most straightforward way is to specialcase zero in your format:

>>> a = -0.0
>>> '%.2f' % ( a if a != 0 else abs(a) )
0.0

However, do note that the str.format method is preferred over % substitutions - the syntax in this case (and in most simple cases) is nearly identical:

>>> '{:.2f}'.format(a if a != 0 else abs(a))

Also note that the more concise a or abs(a) doesn't seem to - even though bool(a) is False.

user278064 · Answer 4 · 2012-06-13T09:26:17.353

1

import re
re.sub("[-+](0\.0+)", r"\1", number)

e.g.:

re.sub("[-+](0\.0+)", r"\1", "-0.0000") // "0.0000"
re.sub("[-+](0\.0+)", r"\1", "+0.0000") // "0.0000"

edited Jun 13 '12 at 09:26

answered Jun 13 '12 at 08:17

user278064

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Ashwini Chaudhary · Answer 5 · 2012-06-13T08:28:14.940

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>>> x= '{0:.2f}'.format(abs(n) if n==0 else n)
>>> print(x) 
0.00

reason for the if condition:

>>> -0.0000==0
True
>>> 0.000==0
True
>>> 0.0==0
True

edited Jun 13 '12 at 08:28

answered Jun 13 '12 at 08:19

Ashwini Chaudhary

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@jamylak Ah! I missed the else condition. – Ashwini Chaudhary Jun 13 '12 at 08:24
You can shorten it to this `'{0:.2f}'.format(abs(n) if n==0 else n)` – jamylak Jun 13 '12 at 08:26
@jamylak suggestion implemented. – Ashwini Chaudhary Jun 13 '12 at 08:28

How to have negative zero always formatted as positive zero in a python string?

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