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-------- Forwarded Message -------- Subject: Re: [Tutor] If loop conditions Date: Wed, 2 Mar 2016 07:31:57 +0530 From: D.V.N.Sarma డి.వి.ఎన్.శర్మ <dvnsa...@gmail.com> To: Alan Gauld <alan.ga...@btinternet.com> The newList = [] statement must be above the for loop just after the function definition. regards, Sarma. On Tue, Mar 1, 2016 at 10:22 PM, Alan Gauld <alan.ga...@btinternet.com> wrote: > On 01/03/16 16:28, Dimitar Ivanov wrote: >> First time using this mailing list so please excuse me in advance if this >> mail is not structured properly. > > No worries, you've done a pretty good job of telling us > what we need to know. > >> In the following exercise, Google requires you to look up words from a list >> and count how many of the words are longer or equal to 2 characters where >> the first and last letter match. >> >> I've been trying to assign string slices to variables and then use those >> variables inside the following if statement: > > You probably don't need slices here. They are cool features > but not always the right thing to use. > >> def match_ends(words): >> + for word in words: >> + length=len(word) >> + newList=[] >> + firstChar=word[0:] >> + lastChar=word[:-1] > > You only want the first and last character, not a slice. > So just use indexes. > > firstChar=word[0] > lastChar=word[-1] > >> + if [ length >= 2 and firstChar == lastChar ]: > > You don;t need the brackets. And in fact in this case > you are creating a list containing the bollean result > of your test. A non empty list (regardless of the > value inside) is always going to be "true"... > > Just write it as: > > if length >= 2 and (firstChar == lastChar): > > The () just make it clear that its > > a and (b == c) > > rather than > > (a and b) == c > >> + newList.append(word) >> + else: >> + break > > break exits the loop, you don't want that, instead you want > to go back to the start of the loop to process the next word. > The command for that is > > continue > >> + newListCount=len(newList) >> + return newListCount > >> Eventually I looked up the solution since I tracked down my problem to how >> I made my if statement and, of course, it turned out to be much simpler >> than usual. >> >> + if len(word) >= 2 and word[0] == word[-1]: >> >> I tried putting brackets around the conditions and that broke the result >> again so I came to wonder what's the difference between statements written >> without brackets and those within brackets (such as my original code block)? > > It all depends on the type of brackets. > Using square brackets as you did creates a list with a single value > > like: [42] or in your case, either [True] or [False] > > The if statement(not loop) then treats any non empty list as True. > > But if you had used () instead of [] then it would probably > work as you expected. > > if (len(word) >= 2 and word[0] == word[-1]): > > But you don;t really need them in Python (unlike C or Java) > > You can however make the intention clearer for your readers > by grouping sub tests with params like: > > if (length >= 2) and (firstChar == lastChar): > > HTH > -- > Alan G > Author of the Learn to Program web site > http://www.alan-g.me.uk/ > http://www.amazon.com/author/alan_gauld > Follow my photo-blog on Flickr at: > http://www.flickr.com/photos/alangauldphotos > > > _______________________________________________ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > https://mail.python.org/mailman/listinfo/tutor _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
