Python 2.x (single expression)
Now, while this is quite easy to figure out for Pythoneers, others might find it at least interesting. If you wonder why there's so many lambdas, I wanted to have maximum underscoreness, but minimal repetition. Who doesn't love underscores? Ideone
(lambda ______________:(lambda ______,_______,________:(lambda _____:(lambda _,___,__,____,_____________:(lambda _________,__________:(lambda ___________,____________:___________(____________,____[_________**(_________+__________)-__________::_________+_________+_________]+_[__________::_________]+__[_________+__________])(____________,______________))((lambda _,__:________(______(_))[__]),(________(__import__(_[_________]+__[_________*_________+__________]+_[_________]))[_[_________:_________+_________]+___[__________/_________]+__[__________]+_____(u'')[__________/_________]+_[_________+__________]])))((_____________(_)+_____________(_))/_____________(_),_____________(_)/_____________(_)))(_____([]),_____({}),_____(None),_____({}.__iter__),lambda _:len(_)))(lambda _:_______(______(_))))((lambda _:_.__class__),(lambda _:_.__name__),(lambda _:_.__dict__)))('Just another Python Hacker\n')
An indented version if you prefer:
(lambda ______________:
(lambda ______,_______,________:
(lambda _____:
(lambda _,___,__,____,_____________:
(lambda _________,__________:
(lambda ___________,____________:
___________(____________,____[_________**(_________+__________)-__________::_________+_________+_________]+_[__________::_________]+__[_________+__________])(____________,______________)) (
(lambda _,__:________(______(_))[__]),
(________(__import__(_[_________]+__[_________*_________+__________]+_[_________]))[_[_________:_________+_________]+___[__________/_________]+__[__________]+_____(u'')[__________/_________]+_[_________+__________]]))) (
(_____________(_)+_____________(_))/_____________(_),
_____________(_)/_____________(_))) (
_____([]),
_____({}),
_____(None),
_____({}.__iter__),
lambda _:len(_))) (
lambda _:_______(______(_)))) (
(lambda _:_.__class__),
(lambda _:_.__name__),
(lambda _:_.__dict__)))('Just another Python Hacker\n')
This defines a function and calls it with 'Just another Python Hacker'. Now, it didn't have to be a function, but I thought it would be more elegant.
f = (lambda ______________:(lambda ______,_______,________:(lambda _____:(lambda _,___,__,____,_____________:(lambda _________,__________:(lambda ___________,____________:___________(____________,____[_________**(_________+__________)-__________::_________+_________+_________]+_[__________::_________]+__[_________+__________])(____________,______________))((lambda _,__:________(______(_))[__]),(________(__import__(_[_________]+__[_________*_________+__________]+_[_________]))[_[_________:_________+_________]+___[__________/_________]+__[__________]+_____(u'')[__________/_________]+_[_________+__________]])))((_____________(_)+_____________(_))/_____________(_),_____________(_)/_____________(_)))(_____([]),_____({}),_____(None),_____({}.__iter__),lambda _:len(_)))(lambda _:_______(______(_))))((lambda _:_.__class__),(lambda _:_.__name__),(lambda _:_.__dict__)))
f('Hello.\n')
f('Just another Python Hacker here.\n')
_2=($_1/*/*); ${_2[34]} -${_2[34]:5:1}'\110\145\154\154\157\54\40\127\157\162\154\144\41'
\$\endgroup\$