Ahh, cool... Thanks for the explanation! Do you want to help develop Dynamic languages on CLR? (http://members.microsoft.com/careers/search/details.aspx?JobID=6D4754DE-11F0-45DF-8B78-DC1B43134038) -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dave Hughes Sent: Friday, April 28, 2006 1:00 PM To: python-list@python.org Subject: Re: Undocumented alternate form for %#f ?
Dino Viehland wrote: > I'm assuming this is by-design, but it doesn't appear to be > documented: > > >>> '%8.f' % (-1) > ' -1' > >>> '%#8.f' % (-1) > ' -1.' > > > The docs list the alternate forms, but there isn't one listed for > f/F. It would seem the alternate form for floating points is > truncate & round the floating point value, but always display the . > at the end. Is that correct? The Python % operator follows the C sprintf function pretty darn closely in behaviour (hardly surprising really, though I've never peeked at the implementation). Hence "man sprintf" can provide some clues here. From man sprintf on my Linux box: # The value should be converted to an ``alternate form''. For o conversions, the first character of the output string is made zero (by prefixing a 0 if it was not zero already). For x and X conversions, a non-zero result has the string `0x' (or `0X' for X conversions) prepended to it. For a, A, e, E, f, F, g, and G conversions, the result will always contain a decimal point, even if no digits follow it (normally, a decimal point appears in the results of those conversions only if a digit follows). For g and G conversions, trailing zeros are not removed from the result as they would otherwise be. For other conversions, the result is undefined. Hence, I don't think it's the # doing the truncating here, but it certainly is producing the mandatory decimal point. If you get rid of the "." in the specification, it uses the default decimal precision (6): >>> "%8f" % (-1) '-1.000000' >>> "%#8f" % (-1) '-1.000000' No difference with the alternate specification here as the precision is non-zero. Again, from man sprintf: The precision [snip] If the precision is given as just `.', or the precision is negative, the precision is taken to be zero. This gives the minimum number of digits to appear for d, i, o, u, x, and X conversions, the number of digits to appear after the radix character for a, A, e, E, f, and F conversions, the maximum number of significant digits for g and G conversions, or the maximum number of characters to be printed from a string for s and S conversions. HTH, Dave. -- -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
