Re: [Tutor] making a list of a custom object
Hi Kate, and welcome!
My replies are interleaved between your questions.
On Fri, Sep 19, 2014 at 04:25:50PM -0500, Kate Reeher wrote:
> I have a custom class called Game, and it has a variable called
> "goals". I'd like to make this a list of custom objects, with various
> information about the goals.
Unfortunately, either your email, or my email, mangled your code below.
I've tried to reconstruct it as well I can, but please don't hesitate to
correct me if I got it wrong.
> class Game:
> goals = {}
>
> class Goal(object):
> def __init__(self,time,goal_by,assist_by,team,is_powerplay ):
> self.time=time
> self.goal_by=goal_by
> self.assist_by=assist_by
> self.team=team
> self.is_powerplay=is_powerplay
>
> Is that Goal class set up correctly?
I can't be absolutely sure, because I'm not sure of your intention, but
it looks correct to me. That's certainly the usual way to set up a
class.
> For an instance of Game called game, is this how you'd set a variable
> of a goal?
> game.goals[i].time= time
You could do it that way to modify an existing goal. (By the way, in
Python circles, we prefer to talk about "attributes" of instances, not
instance variables. If you are interested, I'll give you my standard
rant about this later :-)
Your Game class is a little unusual though. It's not *wrong*, just
unusual, perhaps you intended to do it this way. You have set the Game
class to use a single "class attribute", which means that all
instances will share it. (Actually, the rules are a little more complex
than that, but for now thinking of it as a shared attribute isn't far
wrong.) Was that intentional?
If you're familiar with Java, I think that a class attribute is close to
a Java static variable. (I'm not a Java expert, so I may be wrong.)
If you intend to have multiple Game instances, each with their own
independent set of goals, you would write it like this:
class Game:
def __init__(self):
goals = {}
but I'm not sure why the goals are kept in a dict. That would require
you to keep track of whether each goal is the first, second, third...
goal yourself. I think you want an ordered list:
class Game:
def __init__(self):
goals = []
red_vs_blue = Game()
shirts_vs_skins = Game()
# Add new goals.
red_vs_blue.goals.append(Goal(...)) # Fill in the appropriate args.
shirts_vs_skins.goals.append(Goal(...))
red_vs_blue.goals.append(Goal(...))
# Modify existing goals (but why would you do this?)
red_vs_blue.goals[0].team = 'green'
Because each game has its own list of goals, you can run multiple games
at the same time. You don't have to track the index of the latest goal,
you just append a new goal. You only need to care about the index if you
want to modify an existing goal.
On the other hand, what you originally wrote, with a shared class
attribute, isn't *wrong*. If you absolutely know that there will never
be more than one game at a time, there is no need to bother creating a
Game instance:
class Game:
goals = []
Game.goals.append(Goal(...))
Game.goals.append(Goal(...))
Game.goals[0].team = 'green'
In this case, you can think of the Game class as being almost like a
singleton instance. (Not quite the same, but it does the same job.)
As I said, this is fairly unusual in Python though. Normally you would
stick to standard "one class, multiple instances, each with their own
set of attributes" design.
> I'm finding how python does data classes INCREDIBLY confusing, for
> whatever reason, so any help would be appreciated.
Sorry to hear that. Please don't hesitate to ask about anything
confusing. Giving concrete examples is good, and if you are familiar
with some other language, feel free to say so.
--
Steven
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Re: [Tutor] question 1
Hi Clayton, and welcome. My responses are interleaved between your questions below. On Sat, Sep 20, 2014 at 03:20:09PM -0700, Clayton Kirkwood wrote: > I'm ramping slowly unfortunately. How does one go about knowing which module > to import to make certain functions work? Experience, practice, reading the documentation, experimentation. > I have a read() that fails because > there is no definition for it. I am using the Wing IDE. I have traversed > much of the developer's guide and can't find any certainty. That's a hard question to answer. Where did you get the read() from? I can think of three scenarios: (1) You thought to yourself, "I want to read some data from somewhere, hmmm, this sounds like a job for a function called read(), maybe if I just try it, it will work!" Sadly, no it doesn't. What sort of data are you trying to read, and from where? If you tell us that, we may be able to advise on the correct way to read. (2) You are copying some code from somewhere else, and it includes something like: result = read(abc, xyz) # or whatever You need to go back through the rest of the code until you find a line that looks like either: from something import read or perhaps: read = something or even: def read(this, that, another): ... (3) You're reading a tutorial or book, and it suggests using: result = read(abc, xyz) In which case, read the tutorial a bit more closely. Perhaps earlier in the book they told you where read() comes from? Or maybe they didn't, and the tutorial is just broken, mistaken, buggy or confused. If you show us some of the code around the read() line, we may be able to guess what they meant to say. > Secondarily, why can you import a module without it importing all of its > daughters? And why do you have to use a 'for in to import submodule', why > not ' mport module.sub'? A concrete example might help, because if I'm understanding you correctly, you *can* do exactly that. When you say: import fe.fi.fo.fum Python starts off by importing fe, then fe.fi, then fe.fi.fo, then fe.fi.fo.fum, so that *all* of those dotted names will work. Here's an actual example: >>> import os.path >>> os >>> os.path So even though I only *manually* imported the os.path submodule, Python automatically imported its parent os for me. > Lastly, in some tutorials and else-sourced docs certain lines have a ';' at > the end. This seems to be most often with 'opens' and 'fopen' kind of calls. Are you sure you're reading Python tutorials, not C tutorials? :-) It's not *wrong* to end lines with a semi-colon, but it is poor style. A bit like saying "Um" at the beginning of every sentence. You would have to ask the tutorial author why they are doing such a thing. Do you have a link to an online tutorial that does that, I'm curious to see it for myself. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] question 1
>> Secondarily, why can you import a module without it importing all of its >> daughters? > > The act of importing a module is "recursive": if you import a module, > and that module itself has import statements, then Python will do the > import of the child modules too. And so forth. Hi Deb, Oh! By the way, this echoes that point about recursion from a week or so ago. https://mail.python.org/pipermail/tutor/2014-September/102715.html So yes, recursion shows up at the heart of the Python module import system too. That should have been an obvious example, but I forgot. :P ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] question 1
On Sat, Sep 20, 2014 at 3:20 PM, Clayton Kirkwood wrote: > I’m ramping slowly unfortunately. How does one go about knowing which module > to import to make certain functions work? I have a read() that fails because > there is no definition for it. Specific details may help here. Can you tell us more? What are you trying to do? If you are seeing error messages, please copy exact error message content and present it. Error messages have more than one bit of information: they usually encode some information that folks here can try to interpret. > Secondarily, why can you import a module without it importing all of its > daughters? The act of importing a module is "recursive": if you import a module, and that module itself has import statements, then Python will do the import of the child modules too. And so forth. (You might imagine a system where the "main" module must do all this linkage by itself, rather than do this recursive walk. And there are systems that do work like this! See: https://talks.golang.org/2012/splash.article for Rob Pike's discussion on the Plan 9 compiler, which worked this way. But Python does not do this.) > And why do you have to use a ‘for in to import submodule’, why > not ’import module.sub’? If I'm not mistaken, you _can_ do this. Can you point us to a source where it says you can't? (There are particular style guidelines from certain organizations that prohibit this kind of import, but that prohibition is by convention. That is, it's not because the language disallows it, but because it doesn't fit with the house coding style.) > Lastly, in some tutorials and else-sourced docs certain lines have a ‘;’ at > the end. This seems to be most often with ‘opens’ and ‘fopen’ kind of calls. Huh. Can you point to a reference? Note that third-party documentation (and official documentation!) might be buggy or weird. :P If you can point us to an example, maybe one of us can investigate what's going on there. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Subprocess help
> The command I need to run is "BYPASSROOT=yes > ./octosetupBROADCASTER-linux_i386.bin" Semantically, the command above means: execute "./octosetupBROADCASTER-linux_i386.bin" in an environment that binds BYPASSROOT to "yes". The subprocess.Popen command takes in an optional "env" argument, so that's what you want to provide when creating this new subprocess. Here's a link to the documentation. https://docs.python.org/2/library/subprocess.html#subprocess.Popen So you'll probably want to do something like: envCopy = os.environ.copy() envCopy['BYPASSROOT'] = 'yes' subprocess.Popen(["./octosetupBROADCASTER-linux_i386.bin"], env=envCopy) ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] Subprocess help
Hey all, hope everyone is well. I am trying to write a script that automates a certain task I have recently found myself doing a lot lately. The command I need to run is "BYPASSROOT=yes ./octosetupBROADCASTER-linux_i386.bin" I know how to use subprocess to execute the "./octosetup..." command, however the "BYPASSROOT=yes" is stumping me seeing how it is not really a unix command. I assume it is changing a variable within "octosetup...?" How do I get the "BYPASSROOT=yes" to be included in the subprocess.call? I know i know "root" is bad, but with this, I have no choice. Thanks Bo ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] question 1
I'm ramping slowly unfortunately. How does one go about knowing which module to import to make certain functions work? I have a read() that fails because there is no definition for it. I am using the Wing IDE. I have traversed much of the developer's guide and can't find any certainty. Secondarily, why can you import a module without it importing all of its daughters? And why do you have to use a 'for in to import submodule', why not ' mport module.sub'? Lastly, in some tutorials and else-sourced docs certain lines have a ';' at the end. This seems to be most often with 'opens' and 'fopen' kind of calls. Thanks, Clayton ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] making a list of a custom object
Kate Reeher Wrote in message:
> I have a custom class called Game, and it has a variable called "goals". I'd
> like
> to make this a list of custom objects, with various information about the
> goals.
> class Game:
> goals = {}
That's a class attribute; the others below are instance
attributes. And it's a dict not a list. Perhaps you
want
goals = []
But more likely you're expecting to have more than one game, each
with its own list of goals. In this case you'd want an
initializer method, and within it you'd say
self.goals = []
You'd also want to instantiate at least one game, perhaps like
(outside of the class definition)
game = Game ()
> class Goal(object):
> def __init__(self,time,goal_by,assist_by,team,is_powerplay ):
> self.time=time
> self.goal_by=goal_by
> self.assist_by=assist_by
> self.team=team
> self.is_powerplay=is_powerplay
> This might be where you should append self to the class attrinute.
> Is that Goal class set up correctly?
One of many possibilities.
> For an instance of Game called game, is this how you'd set a
> variable of a goal?
> game.goals[i].time= time
First you have to create the goal.
my_goal = Goal ()
Then you probably need to add that goal to a particular Game.
game.goals.append (my_goal)
Then if you have appended several, and you need to patch the time
of a particular one (the ith one), you might use your statement.
But typically in a game, I'd figure the time for a particular
goal wouldn't change.
--
DaveA
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Re: [Tutor] Help
http://cscircles.cemc.uwaterloo.ca/run-at-home/ On Fri, Sep 19, 2014 at 11:04 AM, Danny Yoo wrote: > On Wed, Sep 17, 2014 at 4:36 PM, Art Pelletier wrote: > > > > I am a beginner with pythons programming I would like to see if their > is a site that has samples programs that I can practice on. > > Hi Art, > > > Yes, there are some good resources you can check out. Here's a link > to some of them: > > https://wiki.python.org/moin/BeginnersGuide/NonProgrammers > > Personally, I like How to Think Like a Computer Scientist: > > http://openbookproject.net/thinkcs/python/english2e/ > > but any of the tutorials in the beginner's guide should be helpful. > > > > Feel free to ask questions here on this mailing list too. > ___ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > https://mail.python.org/mailman/listinfo/tutor > -- Diliup Gabadamudalige http://www.diliupg.com http://soft.diliupg.com/ ** This e-mail is confidential. It may also be legally privileged. If you are not the intended recipient or have received it in error, please delete it and all copies from your system and notify the sender immediately by return e-mail. Any unauthorized reading, reproducing, printing or further dissemination of this e-mail or its contents is strictly prohibited and may be unlawful. Internet communications cannot be guaranteed to be timely, secure, error or virus-free. The sender does not accept liability for any errors or omissions. ** ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] making a list of a custom object
I have a custom class called Game, and it has a variable called "goals". I'd
like to make this a list of custom objects, with various information about the
goals.
class Game: goals = {} class Goal(object): def
__init__(self,time,goal_by,assist_by,team,is_powerplay ):
self.time=time self.goal_by=goal_by
self.assist_by=assist_byself.team=team
self.is_powerplay=is_powerplay
Is that Goal class set up correctly?
For an instance of Game called game, is this how you'd set a variable of a
goal?game.goals[i].time= time
I'm finding how python does data classes INCREDIBLY confusing, for whatever
reason, so any help would be appreciated.
Thanks,Kate
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