Limit decimal digits

[matburnham]

I'm working with latitudes and longitudes in SeeYou CUP format. This is a simple CSV format, but with a somewhat specific DDMM.MMM latitude and longitude format.

For example:

name,code,country,lat,lon,elev,style,rwdir,rwlen,rwwidth,freq,desc,userdata,pics
"Wycombe Air Park - Booker","EGTB",GB,5136.684N,00048.479W,156m,5,,,,

Within this, the lat field is encoded:

Latitude is a field of length 9, where 1-2 characters are degrees, 3-4 characters are minutes, 5 decimal point,
6-8 characters are decimal minutes and 9th character is either N or S. The ellipsoid used is WGS-1984

Char 0	Char 1	Char 2	Char 3	Char 4	Char 5	Char 6	Char 7	Char 8
5	1	0	7	.	8	3	0	N | S
$10^1$ Degrees	$10^0$ Degrees	$10^1$ Minutes	$10^0$ Minutes	.	$10^{-1}$ Minutes	$10^{-2}$ Minutes	$10^{-3}$ Minutes	N | S

I can get very close to what I want, but end up with excessive decimal digits:

>>> latlon.LatLon(51.61140,-0.80798).to_string('%d%%M%%H%')
('5136.6840000000002N', '048.47879999999918W')

Even the example in latlon.py#L123 gives me similar behaviour:

>>> palmyra = LatLon(5.8833, -162.0833)
>>> palmyra.to_string('D')
('5.8833', '-162.0833')
>>> palmyra.to_string('H% %D')
('N 5.8833', 'W 162.0833')
>>> palmyra.to_string('d%_%M')
('5_52.99800000000001', '-162_4.998000000000502')

It would be great if there were a way to specify the number of digits in the format string, and also leading zeros.