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Best way to use globally format

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  Best way to use globally format Cecil Westerhof <Cecil@decebal.nl> - 2015-05-03 17:21 +0200
    Re: Best way to use globally format Peter Otten <__peter__@web.de> - 2015-05-03 18:16 +0200
    Re: Best way to use globally format Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-03 17:32 +0100

#89872 — Best way to use globally format

I have a file where I used a lot of {0}, {1} and {2}. Most but not all
are changed to {0:.3E}, {1:.3E} and {2:.3E}. But when I want to change
the format I come in dependency hell.

I could do something like:
    format = ':.3E'
    fmt0   = '{0' + format + '}
    fmt1   = '{1' + format + '}
    fmt2   = '{2' + format + '}

and replace occurrences of:
    'before {0} after'
with:
    'before ' + fmt0 + ' after'

But that does not really make me happy. Is there a better way?

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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#89879

Cecil Westerhof wrote:

> I have a file where I used a lot of {0}, {1} and {2}. Most but not all
> are changed to {0:.3E}, {1:.3E} and {2:.3E}. But when I want to change
> the format I come in dependency hell.
> 
> I could do something like:
>     format = ':.3E'
>     fmt0   = '{0' + format + '}
>     fmt1   = '{1' + format + '}
>     fmt2   = '{2' + format + '}
> 
> and replace occurrences of:
>     'before {0} after'
> with:
>     'before ' + fmt0 + ' after'
> 
> But that does not really make me happy. Is there a better way?
 
There's limited support for nesting {...}:

>>> "{0:{fmt}}, {1:{fmt}}, {2:{fmt}}".format(1.12345789, 2., 3., fmt=".3E")
'1.123E+00, 2.000E+00, 3.000E+00'
>>> "{0:{fmt}}, {1:{fmt}}, {2:{fmt}}".format(1.12345789, 2., 3., fmt="6.2")
'   1.1,    2.0,    3.0'
>>> "{0:{fmt}}, {1:{fmt}}, {2:{fmt}}".format(1.12345789, 2., 3., fmt="06.2")
'0001.1, 0002.0, 0003.0'

Converting the numbers to string first may be clearer though:

>>> formatted_numbers = [format(x, "010.2") for x in [1.12345789, 2., 3.]]
>>> "{0}, {1}, {2}".format(*formatted_numbers)
'00000001.1, 00000002.0, 00000003.0'

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#89882

Cecil Westerhof <Cecil@decebal.nl> writes:

> I have a file where I used a lot of {0}, {1} and {2}. Most but not all
> are changed to {0:.3E}, {1:.3E} and {2:.3E}. But when I want to change
> the format I come in dependency hell.
>
> I could do something like:
>     format = ':.3E'
>     fmt0   = '{0' + format + '}
>     fmt1   = '{1' + format + '}
>     fmt2   = '{2' + format + '}
>
> and replace occurrences of:
>     'before {0} after'
> with:
>     'before ' + fmt0 + ' after'
>
> But that does not really make me happy. Is there a better way?

'Better' is often a bit tricky.  You could always factor the formatted
printing into a function, but you will have considered that.  You could
pass the format to used to the format function:

  format_for_numbers = '.3E'
  ...
  'x = {0:{nfmt}}, y = {1:{nfmt}}'.format(3.4, 4.5, nfmt=format_for_numbers);

or you could do that with just the width (if that is the variable part):

  'x = {0:.{nwd}E}, y = {1:.{nwd}E}'.format(3.4, 4.5, nwd=4);
  
-- 
Ben.

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