Elementary string-formatting

[Gary Herron]

Odysseus wrote:
> Hello, group: I've just begun some introductory tutorials in Python. 
> Taking off from the "word play" exercise at
>
> <http://www.greenteapress.com/thinkpython/html/book010.html#toc96>
>
> I've written a mini-program to tabulate the number of characters in each 
> word in a file. Once the data have been collected in a list, the output 
> is produced by a while loop that steps through it by incrementing an 
> index "i", saying
>
> print '%2u %6u %4.2f' % \
> (i, wordcounts[i], 100.0 * wordcounts[i] / wordcounts[0])
>   
Using 4.2 is the problem.  The first digit (your 4) give the total
number of characters to use for the number.  Your numbers require at
least 5 characters, two digits,  one decimal point, and two more
digits.  So try 5.2, or 6.2 or 7.2 or higher if your numbers can grow
into the hundreds or thousands or higher.  If you want to try one of the
floating point formats, then your first number must be large enough to
account for digits (before and after) the decimal point, the 'E', and
any digits in the exponent, as well as signs for both the number and the
exponent.

Gary Herron

> My problem is with the last entry in each line, which isn't getting 
> padded:
>
>  1      0 0.00
>  2     85 0.07
>  3    908 0.80
>  4   3686 3.24
>  5   8258 7.26
>  6  14374 12.63
>  7  21727 19.09
>  8  26447 23.24
>  9  16658 14.64
> 10   9199 8.08
> 11   5296 4.65
> 12   3166 2.78
> 13   1960 1.72
> 14   1023 0.90
> 15    557 0.49
> 16    261 0.23
> 17    132 0.12
> 18     48 0.04
> 19     16 0.01
> 20      5 0.00
> 21      3 0.00
>
> I've tried varying the number before the decimal in the formatting 
> string; "F", "g", and "G" conversions instead of "f"; and a couple of 
> other permutations (including replacing the arithmetical expression in 
> the tuple with a variable, defined on the previous line), but I can't 
> seem to get the decimal points to line up. I'm sure I'm missing 
> something obvious, but I'd appreciate a tip -- thanks in advance!
>
> FWIW I'm running
>
> Python 2.3.5 (#1, Oct  5 2005, 11:07:27) 
> [GCC 3.3 20030304 (Apple Computer, Inc. build 1809)] on darwin
>
> from the Terminal on Mac OS X v10.4.11.
>
> P.S. Is there a preferable technique for forcing floating-point division 
> of two integers to that used above, multiplying by "100.0" first? What 
> about if I just wanted a ratio: is "float(n / m)" better than "1.0 * n / 
> m"?
>
>