Floating point -> string conversions

[John Fouhy]

Can someone explain these differences?

>>> from math import pi
>>> pi
3.1415926535897931
>>> type(pi)
<type 'float'>
>>> repr(pi)
'3.1415926535897931'
>>> str(pi)
'3.14159265359'
>>> '%f' % pi
'3.141593'
>>> '%.16f' % pi
'3.1415926535897931'

Why do the string and default floating point representations get rounded?

(and is this documented anywhere?)

-- 
John.