Thank you ALL for your kind help. Yehuda
On Sun, Jan 3, 2016 at 3:12 PM, <tutor-requ...@python.org> wrote: > Send Tutor mailing list submissions to > tutor@python.org > > To subscribe or unsubscribe via the World Wide Web, visit > https://mail.python.org/mailman/listinfo/tutor > or, via email, send a message with subject or body 'help' to > tutor-requ...@python.org > > You can reach the person managing the list at > tutor-ow...@python.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Tutor digest..." > > > Today's Topics: > > 1. To FORMAT or not to (yehudak .) > 2. Re: To FORMAT or not to (Chris Warrick) > 3. Re: To FORMAT or not to (Francois Dion) > 4. Re: To FORMAT or not to (Peter Otten) > 5. Re: To FORMAT or not to (Francois Dion) > 6. Re: To FORMAT or not to (Alan Gauld) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Sun, 3 Jan 2016 14:27:01 +0200 > From: "yehudak ." <katye2...@gmail.com> > To: tutor@python.org > Subject: [Tutor] To FORMAT or not to > Message-ID: > <CAE3ie40p8HDmcMNBQxYf9GSurTPkzWP+jF6=H+Jpxig= > se6...@mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > Hi there, > In a program I wrote the following line (Python 3.5): > > print("You've visited", island, '&', new + ".") > > A programmer told me that it's a bad habit, and I should have used instead: > > print("You've visited {0} {1} {2}{3}".format(island, "&", new, ".")) > > May I understand why? > > > ------------------------------ > > Message: 2 > Date: Sun, 3 Jan 2016 14:04:22 +0100 > From: Chris Warrick <kwpol...@gmail.com> > To: "yehudak ." <katye2...@gmail.com> > Cc: tutor@python.org > Subject: Re: [Tutor] To FORMAT or not to > Message-ID: > <CAMw+j7+RTGqSFOQg= > fohx0xohv8zfc3jjsn3ges2emz-_tr...@mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > On 3 January 2016 at 13:27, yehudak . <katye2...@gmail.com> wrote: > > Hi there, > > In a program I wrote the following line (Python 3.5): > > > > print("You've visited", island, '&', new + ".") > > > > A programmer told me that it's a bad habit, and I should have used > instead: > > > > print("You've visited {0} {1} {2}{3}".format(island, "&", new, ".")) > > > > May I understand why? > > _______________________________________________ > > Tutor maillist - Tutor@python.org > > To unsubscribe or change subscription options: > > https://mail.python.org/mailman/listinfo/tutor > > The programmer was not very intelligent in his use of str.format in > the first place. A more sensible way to write this is: > > print("You've visited {0} & {1}.".format(island, new)) > > Formatting with constant strings is pointless, just include it in the > original input. However, string formatting is not. > > Here are a couple of reasons: > * String formatting works everywhere, but this syntax is specific to > print() ? if you use something else, you might end up producing faulty > code > * The corrected string formatting usage is more readable than the > original print() > * String concatenation with + requires that all arguments are strings, > which is even less readable > * With string formatting, you can apply special formatting to your > inputs (eg. set width, number precision?), which is hard or impossible > with print() > * Using print() with commas adds spaces between all entries, which > might look bad (and it does in this example); the only way to prevent > that is by setting `sep=`, but then you need to remember about a space > after "visited" and around the ampersand? > * Easy to localize (translate into different languages), which is > generally impossible with any of the other options (some languages > might rearrange the sentence!) > > -- > Chris Warrick <https://chriswarrick.com/> > PGP: 5EAAEA16 > > > ------------------------------ > > Message: 3 > Date: Sun, 3 Jan 2016 08:07:06 -0500 > From: Francois Dion <francois.d...@gmail.com> > To: "yehudak ." <katye2...@gmail.com> > Cc: "tutor@python.org" <tutor@python.org> > Subject: Re: [Tutor] To FORMAT or not to > Message-ID: > <CAOLi1KAabyvxJUNgQB1NoOnv__r2Xi_e4Zq= > z6fovtrxqdb...@mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > The answer is neither. The second shows the intent in part but doesn't > quite get it right. > > The intent is to have a string template and insert values in that template: > > print("You've visited {} & {}.".format(island, new) > > This is totally clear what is going to happen. I'm not relying on the > behaviour of print() to format my string. Format does the formating, print > the printing :) > > This separation of concern is a basic building block of good code and is > seen at various scale levels. At a higher level, it is seen in concepts > like MVC. > > Another thing you do by having your string separated, is you could have > them defined elsewhere and have, say, a version in english and a version in > french. > > I;m sure you can see the value. > > Francois > > On Sun, Jan 3, 2016 at 7:27 AM, yehudak . <katye2...@gmail.com> wrote: > > > Hi there, > > In a program I wrote the following line (Python 3.5): > > > > print("You've visited", island, '&', new + ".") > > > > A programmer told me that it's a bad habit, and I should have used > instead: > > > > print("You've visited {0} {1} {2}{3}".format(island, "&", new, ".")) > > > > May I understand why? > > _______________________________________________ > > Tutor maillist - Tutor@python.org > > To unsubscribe or change subscription options: > > https://mail.python.org/mailman/listinfo/tutor > > > > > > -- > raspberry-python.blogspot.com - www.pyptug.org - www.3DFutureTech.info - > @f_dion > > > ------------------------------ > > Message: 4 > Date: Sun, 03 Jan 2016 14:09:24 +0100 > From: Peter Otten <__pete...@web.de> > To: tutor@python.org > Subject: Re: [Tutor] To FORMAT or not to > Message-ID: <n6b6i7$g37$1...@ger.gmane.org> > Content-Type: text/plain; charset="ISO-8859-1" > > yehudak . wrote: > > > Hi there, > > In a program I wrote the following line (Python 3.5): > > > > print("You've visited", island, '&', new + ".") > > > > A programmer told me that it's a bad habit, and I should have used > > instead: > > > > print("You've visited {0} {1} {2}{3}".format(island, "&", new, ".")) > > > > May I understand why? > > I don't see the benefits either. If anything I'd move the constants into > the > format string: > > print("You've visited {island}, & {new}.".format(island=island, new=new)) > > If you use the same names in your format string and your code it should > suffice to read the format string to get an idea of what will be printed. > > In future versions of Python you can simplify it to > > print(f"You've visited {island}, & {new}.") > > https://www.python.org/dev/peps/pep-0498/ > > > > ------------------------------ > > Message: 5 > Date: Sun, 3 Jan 2016 08:10:09 -0500 > From: Francois Dion <francois.d...@gmail.com> > To: Chris Warrick <kwpol...@gmail.com> > Cc: "yehudak ." <katye2...@gmail.com>, "tutor@python.org" > <tutor@python.org> > Subject: Re: [Tutor] To FORMAT or not to > Message-ID: > < > caoli1kb8s53rdkbisfb-b6_-t7jivz96dawfym+z+6ddqny...@mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > And as Chris points out, if there is any possibility that the words will be > in a different order in a different language, use {0}, {1} instead of {}. > > > Francois > > On Sun, Jan 3, 2016 at 8:04 AM, Chris Warrick <kwpol...@gmail.com> wrote: > > > On 3 January 2016 at 13:27, yehudak . <katye2...@gmail.com> wrote: > > > Hi there, > > > In a program I wrote the following line (Python 3.5): > > > > > > print("You've visited", island, '&', new + ".") > > > > > > A programmer told me that it's a bad habit, and I should have used > > instead: > > > > > > print("You've visited {0} {1} {2}{3}".format(island, "&", new, ".")) > > > > > > May I understand why? > > > _______________________________________________ > > > Tutor maillist - Tutor@python.org > > > To unsubscribe or change subscription options: > > > https://mail.python.org/mailman/listinfo/tutor > > > > The programmer was not very intelligent in his use of str.format in > > the first place. A more sensible way to write this is: > > > > print("You've visited {0} & {1}.".format(island, new)) > > > > Formatting with constant strings is pointless, just include it in the > > original input. However, string formatting is not. > > > > Here are a couple of reasons: > > * String formatting works everywhere, but this syntax is specific to > > print() ? if you use something else, you might end up producing faulty > > code > > * The corrected string formatting usage is more readable than the > > original print() > > * String concatenation with + requires that all arguments are strings, > > which is even less readable > > * With string formatting, you can apply special formatting to your > > inputs (eg. set width, number precision?), which is hard or impossible > > with print() > > * Using print() with commas adds spaces between all entries, which > > might look bad (and it does in this example); the only way to prevent > > that is by setting `sep=`, but then you need to remember about a space > > after "visited" and around the ampersand? > > * Easy to localize (translate into different languages), which is > > generally impossible with any of the other options (some languages > > might rearrange the sentence!) > > > > -- > > Chris Warrick <https://chriswarrick.com/> > > PGP: 5EAAEA16 > > _______________________________________________ > > Tutor maillist - Tutor@python.org > > To unsubscribe or change subscription options: > > https://mail.python.org/mailman/listinfo/tutor > > > > > > -- > raspberry-python.blogspot.com - www.pyptug.org - www.3DFutureTech.info - > @f_dion > > > ------------------------------ > > Message: 6 > Date: Sun, 3 Jan 2016 13:12:41 +0000 > From: Alan Gauld <alan.ga...@btinternet.com> > To: tutor@python.org > Subject: Re: [Tutor] To FORMAT or not to > Message-ID: <n6b6o8$isq$1...@ger.gmane.org> > Content-Type: text/plain; charset=utf-8 > > On 03/01/16 12:27, yehudak . wrote: > > Hi there, > > In a program I wrote the following line (Python 3.5): > > > > print("You've visited", island, '&', new + ".") > > > > A programmer told me that it's a bad habit, and I should have used > instead: > > > > print("You've visited {0} {1} {2}{3}".format(island, "&", new, ".")) > > > > May I understand why? > > There are several reasons although your technique is far from > the worst way of doing things. And the format string here would probably > be better written as: > > print("You've visited {0} & {2}.".format(island, new)) > > ie only put the variables as placeholders. > > Why is it better? > 1) It is slightly more performant. String addition and > concatenation are relatively slow processes in Python. > Formatting will usually be slightly faster. This is not > a good reason in itself (and in your case with a single > print it's probably irrelevant) but it's one factor. It > does matter more if you are printing inside a loop with > many variables and long strings. (For example assembling > a web page). So it's a good habit to adopt. > > 2) It improves consistency. You can store the format > string as a variable and then print it out many times > from different parts of your code and it will always > be the same. This makes it much easier to maintain > your program. For example: > > fmtString = "You've visited {0} & {2}." > if foo: > print(fmtString.format(foo,bar)) > else: > print(fmtString.format(baz,bad)) > > Now if you want to change the message you only need to > change the text in one place rather than searching your > code to do an edit. Also the user sees exactly the same > formatting, no extra spaces in one message compared > to another for example. > > 3) formatting provides many extra features to control > justification, leading and spacing. This is especially > important for numeric output where you can define the > number of decimal places, whether a leading sign is > included, padding with zeros etc, etc. You may not > need that initially but if you do have to add it in, > it's trivial with a format string but much more work > if you have lots of hard coded messages all over your > code. > > There may be other reasons too but that should give > you some ideas. > > > -- > 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 > > > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > Tutor maillist - Tutor@python.org > https://mail.python.org/mailman/listinfo/tutor > > > ------------------------------ > > End of Tutor Digest, Vol 143, Issue 4 > ************************************* > _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
