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Groups > comp.lang.python > #79492
| Date | 2014-10-23 02:31 +0100 |
|---|---|
| From | MRAB <python@mrabarnett.plus.com> |
| Subject | Re: I am out of trial and error again Lists |
| References | <rr4g4ah01n2efganet7b8oml8uq1qaf9qc@4ax.com> <m29bu2$8ou$1@dont-email.me> <umdg4apqcmhrgi9preu57247opq5m966g0@4ax.com> <54484635$0$12992$c3e8da3$5496439d@news.astraweb.com> <ophg4adv431bosmq1195tvg55rsn141e73@4ax.com> |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.15100.1414027919.18130.python-list@python.org> (permalink) |
On 2014-10-23 01:10, Seymore4Head wrote: > On Thu, 23 Oct 2014 11:05:08 +1100, Steven D'Aprano > <steve+comp.lang.python@pearwood.info> wrote: > >>Seymore4Head wrote: >> >>> Those string errors were desperate attempts to fix the "append" error >>> I didn't understand. >> >>Ah, the good ol' "make random changes to the code until the error goes away" >>technique. You know that it never works, right? >> >>Start by *reading the error message*, assuming you're getting an error >>message. I'm the first person to admit that Python's error messages are not >>always as clear as they should be, especially syntax errors, but still >>there is a lot of information that can be gleamed from most error messages. >>Take this attempt to use append: >> >>py> mylist.append(23) >>Traceback (most recent call last): >> File "<stdin>", line 1, in <module> >>NameError: name 'mylist' is not defined >> >>That tells me that I have forgotten to define a variable mylist. So I fix >>that: >> >>py> mylist = 23 >>py> mylist.append(23) >>Traceback (most recent call last): >> File "<stdin>", line 1, in <module> >>AttributeError: 'int' object has no attribute 'append' >> >> >>That tells me that I can't append to a int. After googling for "Python >>append" I learn that I can append to a list, so I try again: >> >>py> mylist = [] >>py> mylist.append(23) >>py> print(mylist) >>[23] >> >> >>Success! >> >>If you are familiar with other programming languages, it might help to think >>of append() as being like a procedure in Pascal, for example. You call >>append() with an argument, but don't expect a return result. >> >>Technically, *all* functions and methods in Python return something, even if >>just the special value None, which can lead to "Gotchas!" like this one: >> >>py> mylist = mylist.append(42) # Don't do this! >>py> print(mylist) # I expect [23, 42] but get None instead. >>None >> >>Oops. One of the small annoyances of Python is that there is no way to tell >>ahead of time, except by reading the documentation, whether something is a >>proper function that returns a useful value, or a procedure-like function >>that returns None. That's just something you have to learn. >> >>The interactive interpreter is your friend. Learn to experiment at the >>interactive interpreter -- you do know how to do that, don't you? If not, >>ask. At the interactive interpreter, if a function or method returns a >>value, it will be printed, *except for None*. So a function that doesn't >>print anything might be procedure-like, and one which does print something >>might not be: >> >>py> mylist = [1, 5, 2, 6, 4, 3] >>py> sorted(mylist) # proper function returns a value >>[1, 2, 3, 4, 5, 6] >>py> mylist.sort() # procedure-like function returns None >>py> print(mylist) # and modifies the list in place >>[1, 2, 3, 4, 5, 6] > > I am going to get around to learning the interpreter soon. > Why wait? You're trying to learn the language _now_, and checking things interactively will help you.
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I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 16:30 -0400
Re: I am out of trial and error again Lists Joel Goldstick <joel.goldstick@gmail.com> - 2014-10-22 16:57 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 17:04 -0400
Re: I am out of trial and error again Lists sohcahtoa82@gmail.com - 2014-10-22 14:35 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 17:38 -0400
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-22 22:28 +0100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 18:30 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 18:32 -0400
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-22 23:55 +0100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 19:26 -0400
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-23 00:44 +0100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 20:02 -0400
Re: I am out of trial and error again Lists MRAB <python@mrabarnett.plus.com> - 2014-10-23 02:29 +0100
Re: I am out of trial and error again Lists alex23 <wuwei23@gmail.com> - 2014-10-23 11:37 +1000
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 21:52 -0400
Re: I am out of trial and error again Lists Larry Hudson <orgnut@yahoo.com> - 2014-10-22 19:58 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 23:05 -0400
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-22 20:16 -0700
Re: I am out of trial and error again Lists Terry Reedy <tjreedy@udel.edu> - 2014-10-23 02:31 -0400
Re: I am out of trial and error again Lists MRAB <python@mrabarnett.plus.com> - 2014-10-23 00:09 +0100
Re: I am out of trial and error again Lists Larry Hudson <orgnut@yahoo.com> - 2014-10-23 00:10 -0700
Re: I am out of trial and error again Lists Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-23 09:23 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 10:00 -0400
Re: I am out of trial and error again Lists Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-23 20:23 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 09:53 -0400
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-23 09:15 +0000
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 10:04 -0400
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-23 15:55 +0000
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 13:01 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 13:07 -0400
Re: I am out of trial and error again Lists Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-23 13:39 -0600
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 16:15 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 16:44 -0400
Re: I am out of trial and error again Lists MRAB <python@mrabarnett.plus.com> - 2014-10-23 22:03 +0100
Re: I am out of trial and error again Lists Larry Hudson <orgnut@yahoo.com> - 2014-10-23 19:13 -0700
Re: I am out of trial and error again Lists Terry Reedy <tjreedy@udel.edu> - 2014-10-23 23:14 -0400
Re: I am out of trial and error again Lists Chris Angelico <rosuav@gmail.com> - 2014-10-24 14:32 +1100
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-23 21:56 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 10:38 -0400
Re: I am out of trial and error again Lists Chris Angelico <rosuav@gmail.com> - 2014-10-25 01:51 +1100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 11:04 -0400
Re: I am out of trial and error again Lists Chris Angelico <rosuav@gmail.com> - 2014-10-25 02:13 +1100
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 08:56 -0700
Re: I am out of trial and error again Lists Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-24 10:35 -0600
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 10:10 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 12:37 -0400
Re: I am out of trial and error again Lists Chris Angelico <rosuav@gmail.com> - 2014-10-25 03:47 +1100
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 09:56 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 13:03 -0400
Re: I am out of trial and error again Lists "Albert Visser" <albert.visser@gmail.com> - 2014-10-24 19:18 +0200
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 13:23 -0400
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 10:42 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 13:42 -0400
Re: I am out of trial and error again Lists Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-24 11:52 -0600
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 14:15 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 14:20 -0400
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-24 19:40 +0100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 15:07 -0400
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-24 21:49 +0000
Re: I am out of trial and error again Lists Larry Hudson <orgnut@yahoo.com> - 2014-10-24 23:46 -0700
Re: I am out of trial and error again Lists Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-25 08:17 -0600
Re: I am out of trial and error again Lists Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-25 14:47 -0400
Re: I am out of trial and error again Lists sohcahtoa82@gmail.com - 2014-10-24 11:57 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 15:09 -0400
Re: I am out of trial and error again Lists sohcahtoa82@gmail.com - 2014-10-24 12:25 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 15:33 -0400
Re: I am out of trial and error again Lists sohcahtoa82@gmail.com - 2014-10-24 12:55 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 16:00 -0400
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-24 21:19 +0000
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 17:35 -0400
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-24 23:23 +0000
Re: I am out of trial and error again Lists Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-25 14:37 -0400
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-24 19:33 +0100
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 09:54 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 13:04 -0400
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 10:17 -0700
Re: I am out of trial and error again Lists Dave Angel <davea@davea.name> - 2014-10-24 18:09 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 18:27 -0400
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 16:01 -0700
Re: I am out of trial and error again Lists Terry Reedy <tjreedy@udel.edu> - 2014-10-24 20:27 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 20:42 -0400
Re: I am out of trial and error again Lists Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-24 11:05 -0600
Re: I am out of trial and error again Lists Chris Angelico <rosuav@gmail.com> - 2014-10-25 04:10 +1100
Re: I am out of trial and error again Lists Larry Hudson <orgnut@yahoo.com> - 2014-10-24 23:04 -0700
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-24 20:37 +0000
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 16:58 -0400
Re: I am out of trial and error again Lists alister <alister.nospam.ware@ntlworld.com> - 2014-10-24 21:07 +0000
Re: I am out of trial and error again Lists Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-24 15:11 -0600
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-24 23:21 +0000
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 19:48 -0400
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-24 21:48 +0000
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 18:14 -0400
Re: I am out of trial and error again Lists Grant Edwards <invalid@invalid.invalid> - 2014-10-25 15:01 +0000
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-25 20:51 +0000
Re: I am out of trial and error again Lists Larry Hudson <orgnut@yahoo.com> - 2014-10-24 19:16 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 22:41 -0400
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-25 08:25 +0100
Re: I am out of trial and error again Lists Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-25 15:10 -0400
Re: I am out of trial and error again Lists Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-25 14:23 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-25 14:42 -0400
Re: I am out of trial and error again Lists Terry Reedy <tjreedy@udel.edu> - 2014-10-25 18:48 -0400
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-26 00:25 +0100
Re: I am out of trial and error again Lists Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-26 01:08 -0400
Re: I am out of trial and error again Lists Terry Reedy <tjreedy@udel.edu> - 2014-10-26 17:44 -0400
Re: I am out of trial and error again Lists Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-26 20:57 -0400
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-22 22:43 +0000
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 19:11 -0400
The “trials” in “trial and error” should be as simple as possible (was: I am out of trial and error again Lists) Ben Finney <ben+python@benfinney.id.au> - 2014-10-23 10:59 +1100
Re: I am out of trial and error again Lists Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-23 11:05 +1100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 20:10 -0400
Re: I am out of trial and error again Lists MRAB <python@mrabarnett.plus.com> - 2014-10-23 02:31 +0100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 21:35 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-22 21:57 -0400
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-23 08:20 +0100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 10:01 -0400
Re: I am out of trial and error again Lists Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-23 01:56 -0600
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-23 09:09 +0100
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-23 06:42 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 10:03 -0400
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-23 08:35 -0700
Re: I am out of trial and error again Lists giacomo boffi <pecore@pascolo.net> - 2014-10-23 16:25 +0200
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 10:29 -0400
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-23 16:00 +0000
Re: I am out of trial and error again Lists giacomo boffi <pecore@pascolo.net> - 2014-10-23 16:40 +0200
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-23 10:46 -0400
Re: I am out of trial and error again Lists giacomo boffi <pecore@pascolo.net> - 2014-10-24 17:56 +0200
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-23 09:21 +0000
Re: I am out of trial and error again Lists Tobiah <toby@tobiah.org> - 2014-10-23 07:51 -0700
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-24 08:05 +0100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 10:47 -0400
Re: I am out of trial and error again Lists mm0fmf <none@mailinator.com> - 2014-10-24 22:06 +0100
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-24 09:12 +0100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 10:48 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 18:26 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 18:58 -0400
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 16:27 -0700
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 19:48 -0400
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 19:57 -0400
Re: I am out of trial and error again Lists MRAB <python@mrabarnett.plus.com> - 2014-10-25 01:20 +0100
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 20:37 -0400
Re: I am out of trial and error again Lists Cameron Simpson <cs@zip.com.au> - 2014-10-25 11:52 +1100
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 20:46 -0700
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 21:09 -0700
Re: I am out of trial and error again Lists Ben Finney <ben+python@benfinney.id.au> - 2014-10-25 15:25 +1100
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 22:40 -0700
Re: I am out of trial and error again Lists Chris Angelico <rosuav@gmail.com> - 2014-10-25 16:49 +1100
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-24 22:55 -0700
Re: I am out of trial and error again Lists Chris Angelico <rosuav@gmail.com> - 2014-10-25 17:03 +1100
Re: I am out of trial and error again Lists Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-25 18:44 +1100
Re: I am out of trial and error again Lists Rustom Mody <rustompmody@gmail.com> - 2014-10-25 10:24 -0700
Side-effects [was Re: I am out of trial and error again Lists] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-26 17:12 +1100
Re: Side-effects [was Re: I am out of trial and error again Lists] Chris Angelico <rosuav@gmail.com> - 2014-10-26 17:42 +1100
Re: I am out of trial and error again Lists giacomo boffi <pecore@pascolo.net> - 2014-10-27 22:26 +0100
Re: I am out of trial and error again Lists Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-25 00:27 +0100
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-24 23:35 +0000
Re: I am out of trial and error again Lists Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-24 20:15 -0400
Re: I am out of trial and error again Lists Denis McMahon <denismfmcmahon@gmail.com> - 2014-10-25 22:15 +0000
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