Negative integers and string formating

Steven D'Aprano steve at REMOVEME.cybersource.com.au
Tue Oct 24 03:44:05 CEST 2006


Problem: I have an application where I need to print integers differently
depending on whether they are positive or negative. To be more specific, I
have to print something that looks like:

"something + 1"
"something - 1" 

Note the space between the sign and the number. If I didn't need that
space, I would have no problem. Yes, I do need that space.

I build the format string on the fly, then pass it to another function
which actually fills in the values. Simplified example:

def format(n):
    if n > 0:
        return "something positive + %(argument)d"
        # real code has a good half-dozen named keys
    elif n < 0:
        return "something negative - %(argument)d"
    else:
        return "blank"

def display(**kwargs):
    fs = format(kwargs['argument'])
    return fs % kwargs



This works fine for positive and zero values:

>>> display(argument=0)
'blank'
>>> display(argument=1)
'something positive + 1'

but not for negative, due to the extra negative sign:

>>> display(argument=-1)
'something negative - -1'

Are there any string formatting codes that will place a space between the
sign and the number?



-- 
Steven




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