Bugfix: forcibly flush sys.stdout after manual write

Under python 2 it seems that writing to stdout implicitly flushes, but
this behavior is not preserved by Python 3. As a result a manual flush
is required in ordero to ensure that my "->>" prompt is displayed.
Bugfix: correct for Python 3 lambda syntax

In Python 2 it is legal to say lambda(x):, in Py3 lambda may _not_
take parenthesized arguments.
(lambda (x y) ..) is written lambda x,y: ...
just to add insult to the fact that python doesn't have real lambdas.