Max Rybinsky <[EMAIL PROTECTED]> wrote: ... > >>> funcs = [lambda n: x * y / n for x, y in a] ... > It seems, all functions have x and y set to 9. > What's wrong with it? Is it a bug?
It's known as *late binding*: names x and y are looked up when the lambda's body is executing, and at that time they're both set to the value 9. You appear to have expected *early binding*, with the names being somehow looked up at the time the lambda keyword executed, but that's just not Python semantics (and would interfere with many other cases where late binding is exactly what one wants). You've already indicated what's probably the best solution -- a factory function instead of the lambda. There are other ways to request early binding, and since you appear to value compactness over clarity the most compact way is probably: funcs = [lambda n, x=x, y=y: x*y/n for x, y in a] it's not perfect, because the resulting functions can take up to 3 arguments, so that if you called funcs[1](2,3) you'd get an unwanted result rather than a TypeError exception. If you're keen on getting the exception in such cases, you can use a lambda factory in the same role as the much clearer and more readable factory function you had (which I keep thinking is the _sensible_ solution)...: funcs = [ (lambda x,y: lambda n: x*y/n)(x,y) for x,y in a ] Alex -- http://mail.python.org/mailman/listinfo/python-list
