On May 9, 8:57 am, [EMAIL PROTECTED] wrote: > On May 8, 6:11 pm, Duncan Booth <[EMAIL PROTECTED]> wrote: > > > > > No, no, no, no, no! > > Geez. Go easy. > > > > > You have got it entirely wrong here. Your XOR function simply returns a > > function which gives you the result of xoring the parameters AT THE TIME > > WHEN YOU ORIGINALLY CREATED IT. I'm guessing that you had already set > > cream and icecream (otherwise the call to XOR would have thrown an > > exception) and at leas one was true. Try setting them both False at the > > beginning: > > > >>> cream = False > > >>> icecream = False > > >>> topping = XOR( cream, icecream) > > >>> cream = True > > >>> icecream = False > > >>> print topping() > > > False > > Ok. I understand this better now. I did say I found the documentation > rather terse on this. > > > Using a lambda was a completely pointless exercise here, you could have > > just returned the result directly: > > If I try out a new language, I try to exercise those parts of the > language that are new to me. Now I saw lambdas, an interesting > structure I hadn't seen before. So I tried them out. I get to learn a > little at the same time as scripting. That was the "point". I only > get to optimise my use of a language by trying out various corners of > it. > > > > > def TFF(x,y,z) : > > return x and not y and not z > > > AddOnly = TFF( options.AddAction, options.ReplaceAction, > > options.DeleteAction ) > > DeleteOnly = TFF( options.DeleteAction, options.AddAction, > > options.ReplaceAction ) > > ReplaceOnly = TFF( options.ReplaceAction, options.AddAction, > > options.DeleteAction ) > > > if not (DeleteOnly or AddOnly or ReplaceOnly): > > print "Error: Exactly one of [ --add | --replace | --delete ] > > allowed. " > > parser.print_help() > > exit > > > which boils down to: > > > if (options.AddAction + options.ReplaceAction + > > options.DeleteAction) != 1: > > print "Error: ..." > > Indeed, there are many ways this could be done. Some are more > concise, some are more efficient. As I said, I did it the way I did > it to try out lambdas. Your way achieves the result, rather elegantly > I think, but teaches me nothing about using lambdas. > > Pardon my tetchiness, but it is a little hard to receive such blunt > and inflexible replies to my posts. > > Both the responses offer lambda free alternatives. That's fine, and > given the terse documentation and problems that I had understanding > them, I would agree. So what applications are lambdas suited to? I > think the parameterised function model is one. > What else?
Lambda can actually be safely removed from python and no other features would be missing. It is always possible to create a def version of any lambda, so lambda is useless. It is just a convenience for the times where we're just too lazy to invent a name and find a place to place the def, instead just inlining the function. -- http://mail.python.org/mailman/listinfo/python-list
