[Python-Dev] One more proposed formatting change for 3.1

Mark Dickinson dickinsm at gmail.com
Tue Apr 28 13:56:59 CEST 2009

Here's one more proposed change, this time for formatting
of floats using format() and the empty presentation type.
To avoid repeating myself, here's the text from the issue
I just opened:


In all versions of Python from 2.6 up, I get the following behaviour:

>>> format(123.456, '.4')
>>> format(1234.56, '.4')
>>> format(12345.6, '.4')

The first and third results are as I expect, but the second is somewhat
misleading: it gives 5 significant digits when only 4 were requested,
and moreover the last digit is incorrect.

I propose that Python 2.7 and Python 3.1 be changed so that the output
for the second line above is '1.235e+03'.

This issue seems fairly clear cut to me, and I doubt that there's been
enough uptake of 'format' yet for this to risk significant breakage.  So
unless there are objections I'll plan to make this change before this
weekend's beta.


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