On Mon, Sep 12, 2011 at 4:43 AM, Ethan Furman <et...@stoneleaf.us> wrote: > Chris Angelico wrote: >> >> And I'd do this with a lambda, but that's just me. Of course, if your >> logic is more complicated, it makes more sense to keep it in a named >> function, but a single conditional call can fit nicely into a lambda. > > Lambdas are great when needed, but if don't *need* it, and you have more > than a few, debugging can be a nightmare... "Okay, so this is function > <lambda>... and that is function <lambda>... and over here we also have > function <lambda>... ARGH!"
Yeah, they can be like the Bruces sketch at times. A lambda is basically a function defined in an expression. For instance: def add_one(x): return x+1 is (practically) the same as: add_one = lambda x: x+1 In each case, you can call that function and will get back a value. The advantage of lambdas is that, in a list comprehension or map call, the code is right there instead of being elsewhere in a def statement. But as you can see, they quickly become hard to read: [j+2 for i in [[1,2,3],[4,5,6],[7,8,9]] for j in (lambda x: [q+10 for q in x])(i)] Their main advantage isn't in list comps, where you can already use arbitrary expressions, but in calls that require a function as an argument. The map() function is very similar to a generator expression, but it can iterate over multiple iterables at once: >>> list(map(lambda x,y: x+y,[1,2,3],[40,50,60])) [41, 52, 63] Note how the lambda keeps the code right there, whereas a def would separate it out. It's obvious from this one expression that it's adding successive corresponding pairs. Hope that helps! ChrisA -- http://mail.python.org/mailman/listinfo/python-list
