In all current versions of Python, the str or repr of a float always 
includes *either* an exponent, or a decimal point and at least one digit 
after the decimal point.

I propose making the str or repr of a complex number behave in the same 
way.  That is, instead of

>>> 2+4j
(2+4j)

we'd have:

>>> 2+4j
(2.0+4.0j)

The aims are to make complex representation more consistent with float 
representation, retain the visual reminder that the pieces of a complex 
number are floats (to me, 2+4j looks like a Gaussian integer rather than 
a complex number), simplify the implementation a little, and remove the 
ugliness where floats switch from normal to exponential notation at 
1e11, but complex numbers switch at 1e12.

See

http://mail.python.org/pipermail/python-dev/2009-April/089030.html

for some additional discussion.