Extensible, Single-Line Fizzbuzz in a Tweet

By Chris Clark, 11/01/2012, in Code & tutorials

Yep, it's a fizzbuzz blog post! I can hardly believe I've gone this long without ever doing one.

I was thinking about hiring and what I would do if someone asked me fizzbuzz, and I think I would have used it as an opportunity to show off some engineering practices. Basically, I'd write unit tests and make it extensible. Before I knew it this was no longer a thought exercise and I was fiddling around in IPython Notebook (which is great for this sort of thing) and created very explicit implementation:

swaps = []
swaps.append((3, "fizz"))
swaps.append((5, "buzz"))
for i in xrange(1,101):
    out = ""
    for s in swaps:
        if i % s[0] == 0:
            out += s[1]
    if not len(out):
        out = i
    print out

I like this approach because it's reasonably extensible - just add more tuples to the list of swaps and everything works. Want to print "bazz" for multiples of 4? Just add swaps.append((4, "bazz")).

But it's pretty boring. As I'm always trying to get better at writing idiomatic Python, I started swapping in some more Pythonic constructs:

swaps = []
swaps.append((3, "fizz"))
swaps.append((5, "buzz"))
for i in xrange(1,101):
    out = "".join([s[1] if i % s[0] == 0 else "" for s in swaps])
    print out or i

Now of course, I'm hooked and decide I want to shrink it down to fit in a Tweet. Not terribly difficult, just rename variables, eliminate spaces, and condense variable declarations:

for i in range(1,101):
    o="".join([x[1] if i%x[0]==0 else "" for x in s])
    print o or i

And I still have 21 characters to spare. But Twitter doesn't support linebreaks so if I were to Tweet it, no one could run it without guessing at the indentation and linebreaks. The semicolon trick almost works but only gets me this far (the line break after the semicolon is still required):

for i in range(1,101): o="".join([x[1] if i%x[0]==0 else "" for x in s]);print o or i

This is because Python won't let you inline control flow statements. I don't want to move the variable declaration inline because it contradicts any semblance of extensibility still here (I know this is silly, but ya gotta have yer principles), so I have to get creative.

Instead of a loop, a construct like map(lambda, range(1,101)) will work. Again though, a little creativity is in order because "print" is a statement and can't appear inside a lambda (only expressions are allowed). Instead I can use sys.stdout.write. Finally, I added a neat little trick to avoid the if/else (multiplying a string by a boolean value) and wound up with this functioning, extensible, single line Fizzbuzz that fits in a Tweet:

s=[(3,"fizz"),(5,"buzz")];map(lambda i: sys.stdout.write("%s\n" % ("".join((i%x[0]==0)*x[1] for x in s) or i)), range(1,101))

Sure there are shorter versions out there, but I had a lot of fun with my version and picked up a couple additional Python tricks on the way.

(for completeness, if I caved and inlined the variable declaration, I get this, which is pretty darn short)

for i in range(1,101):print "".join((i%x[0]==0)*x[1] for x in [(3,"fizz"),(5,"buzz")]) or i

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