This seems to be wrong:

>>> "{0:.2}".format(1.2345)
'1.2'

The same happens for format specifiers "g" and "n", but not for "f":

>>> "{0:.2f}".format(1.2345)
'1.23'

With empty format specifier it can even get really wrong:

>>> "{0:.1}".format(1.2345)
'1.0'

Just found it documented for the % operator: There precision is number
of digits before and after decimal point for format "g". 

But then the documentation for 2.6 is wrong:

"The precision is a decimal number indicating how many digits should be
displayed after the decimal point for a floating point value."

Fixed docs in r65099.