Fantastic explanation everyone. Thanks a lot. Looking forward to using lambda going forward.
~ Ajit Deshpande On Sat, Mar 19, 2011 at 6:07 PM, Steven D'Aprano <st...@pearwood.info>wrote: > Ajit Deshpande wrote: > >> I am trying to figure out where lambda functions can be useful. Has anyone >> used them in real world? >> > > Of course. lambdas are especially useful for callback functions, which are > especially common when doing GUI programming. > > > > From my reading so far, I hear people claim that lambda can be a useful >> replacement for small functions. Most examples didn't make much sense to >> me. Why would anyone use a one liner anonymous function, if you never plan >> to use it elsewhere? >> > > That's precisely the point -- why would you define a non-anonymous function > that you only use once? > > def spam(x): > return x + something > > register_handler(spam) # Provide a callback to some part of your app > # never use spam again > > > is better written as: > > register_handler(lambda x: x+something) > > > > You would then be implementing the logic directly in >> the line, isn't it?. Functions are useful if they plan to get called >> multiple times within your code. >> > > That's often the case, but not necessarily. > > > > > For example: >> >> add_one = lambda x: x + 1 >> > > This defines a function "add_one". This is equivalent to writing: > > def add_one(x): > return x+1 > > > In real world, why would I use a lambda for this. I would simply do: >> >> add_one = x + 1 >> > > This takes the current value of x, adds one to it, and assigns it to the > very badly named variable "add_one". > > > > Can you provide some useful use cases for lambda functions? >> > > Sorting with comparison or key functions. > min or max with a key function. > Callbacks. > map > reduce > Solving numerical equations. > > There are probably others, but they're the obvious ones. > > Here's an example you can try: > > text = """Li Europan lingues es membres del sam familie. Lor separat > existentie es un myth. Por scientie, musica, sport etc, litot Europa usa li > sam vocabular. Li lingues differe solmen in li grammatica, li pronunciation > e li plu commun vocabules. Omnicos directe al desirabilite de un nov lingua > franca: On refusa continuar payar custosi traductores.""" > words = text.lower().split() > sorted(words) # sort in alphabetical order > > > Now suppose you want to sort by the number of vowels. Here's how you can do > it with an anonymous key function: > > sorted(words, key=lambda word: sum(word.count(c) for c in 'aeiou')) > > > -- > Steven > > > _______________________________________________ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor >
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