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Phosphorus and Lime

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Monday, June 02, 2008
A Pythonic Tribute to xkcd
This started with a simple question: "is it possible to call isset($foo) in python like in php?" This is probably going about it ass-backwards, or at least it's asking the wrong question. But then genius of this magnitude doesn't arise from asking the right question.

In the end, I had an answer to my question. I had, perhaps, the stupidest stupid lambda trick ever. And I had a loving pythonic tribute to xkcd (for a loving xkcd tribute to python, click here):

#!/usr/bin/python

"""
a pythonic tribute to xkcd
http://phosphorusandlime.blogspot.com/2008/06/pythonic-tribute-to-xkcd.html
"""

xkcd = lambda x,k,c,d: (({k:False},c,d,c)[int(''.join([str(int(k in i)) for i in [d,c]]),2)])[k] or x

X = 'webcomic'
K = 'romance'
C = {'romance': 'at last!', 'sarcasm':'grep -R soulmate /'}
D = {'math':complex(6,9j), 'language':'to be or not to be'}

print xkcd(X,'language',C,D)
print xkcd(X,'math',{'math':1+1},D)
print xkcd(X,'microsoft',C,D)
print xkcd(X,K,C,D)


# Alternate version
xkcd = lambda x,k,c,d: c.get(k,d.get(k,x))
print xkcd(X,'language',C,D)
print xkcd(X,'math',{'math':1+1},D)
print xkcd(X,'microsoft',C,D)
print xkcd(X,K,C,D)


There are a couple moments of sheer pythonic bliss in there if you pay attention.

Still haven't figured out what it does? Here's a hint:

<?php print $x = ( isset($C[$k]) ) ? $C[$k] : ( isset($D[$k]) ? $D[$k] : $x); ?>


update: added extra c for case where both dicts contain key as pointed out here and added test case

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