Re: Why all the __double_underscored_vars__?
On Sat, 08 Aug 2009 12:11:19 +, kj wrote: In mailman.4446.1249683227.8015.python-l...@python.org Chris Rebert c...@rebertia.com writes: The double-underscores indicate that the Python interpreter itself usually is the caller of the method, and as such some level of magic may be associated with it. Other languages have you do the equivalent of `def +():` or `def operator +()` to override an operator, the keyword or symbol serving a similar warning that here be magic. In this case, then I hope that some of these __items__ get demoted to a more mundane level, so that the notion of magic doesn't get trivialized by everyday idioms like: if __name__ == '__main__': # etc But that is magic, and just because it's magic doesn't mean it's not useful every day. I don't see what's so difficult about telling your students that double underscore names have special meaning to the Python interpreter. That doesn't mean you're forbidden from using them, or that you have to use them, it just means that they have a special meaning to the interpreter, and you usually don't call them directly. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Why all the __double_underscored_vars__?
In mailman.4446.1249683227.8015.python-l...@python.org Chris Rebert c...@rebertia.com writes: The double-underscores indicate that the Python interpreter itself usually is the caller of the method, and as such some level of magic may be associated with it. Other languages have you do the equivalent of `def +():` or `def operator +()` to override an operator, the keyword or symbol serving a similar warning that here be magic. In this case, then I hope that some of these __items__ get demoted to a more mundane level, so that the notion of magic doesn't get trivialized by everyday idioms like: if __name__ == '__main__': # etc There are a few in this category... I figure that they are cases of atavistic magic. I bring this up because I find it quite difficult to explain to my students (who are complete newcomers to programming) all the __underscored__ stuff that even rank noobs like them have to deal with. (Trust me, to most of them your reply to my post would be as clear as mud.) This suggests to me that there's something a bit unnatural about some of these __items__. Anyway, thanks for your post. I see your point. kynn -- http://mail.python.org/mailman/listinfo/python-list
Re: Why all the __double_underscored_vars__?
On Sat, Aug 8, 2009 at 9:11 PM, kjno.em...@please.post wrote: In mailman.4446.1249683227.8015.python-l...@python.org Chris Rebert c...@rebertia.com writes: The double-underscores indicate that the Python interpreter itself usually is the caller of the method, and as such some level of magic may be associated with it. Other languages have you do the equivalent of `def +():` or `def operator +()` to override an operator, the keyword or symbol serving a similar warning that here be magic. In this case, then I hope that some of these __items__ get demoted to a more mundane level, so that the notion of magic doesn't get trivialized by everyday idioms like: if __name__ == '__main__': # etc There are a few in this category... I figure that they are cases of atavistic magic. I bring this up because I find it quite difficult to explain to my students (who are complete newcomers to programming) all the __underscored__ stuff that even rank noobs like them have to deal with. (Trust me, to most of them your reply to my post would be as clear as mud.) Maybe your students do not need to know about it, at least at the beginning ? I heavily use python, and do not use the underscore methods so much most of the time, except for __init__, cheers, David -- http://mail.python.org/mailman/listinfo/python-list
Re: Why all the __double_underscored_vars__?
These special methods are not meant to be used or known to beginners. They aren't even meant to be called directly (in most cases). They are either operator overloading methods or behavior customization methods. In my opinion, in the meta programming realm. Should probably in advanced topic or something. On Sat, Aug 8, 2009 at 5:11 AM, kj no.em...@please.post wrote: In mailman.4446.1249683227.8015.python-l...@python.org Chris Rebert c...@rebertia.com writes: The double-underscores indicate that the Python interpreter itself usually is the caller of the method, and as such some level of magic may be associated with it. Other languages have you do the equivalent of `def +():` or `def operator +()` to override an operator, the keyword or symbol serving a similar warning that here be magic. In this case, then I hope that some of these __items__ get demoted to a more mundane level, so that the notion of magic doesn't get trivialized by everyday idioms like: if __name__ == '__main__': # etc There are a few in this category... I figure that they are cases of atavistic magic. I bring this up because I find it quite difficult to explain to my students (who are complete newcomers to programming) all the __underscored__ stuff that even rank noobs like them have to deal with. (Trust me, to most of them your reply to my post would be as clear as mud.) This suggests to me that there's something a bit unnatural about some of these __items__. Anyway, thanks for your post. I see your point. kynn -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Why all the __double_underscored_vars__?
In mailman.4455.1249736560.8015.python-l...@python.org David Cournapeau courn...@gmail.com writes: On Sat, Aug 8, 2009 at 9:11 PM, kjno.em...@please.post wrote: In mailman.4446.1249683227.8015.python-l...@python.org Chris Rebert cl= p...@rebertia.com writes: The double-underscores indicate that the Python interpreter itself usually is the caller of the method, and as such some level of magic may be associated with it. Other languages have you do the equivalent of `def +():` or `def operator +()` to override an operator, the keyword or symbol serving a similar warning that here be magic. In this case, then I hope that some of these __items__ get demoted to a more mundane level, so that the notion of magic doesn't get trivialized by everyday idioms like: if __name__ =3D=3D '__main__': =C2=A0 =C2=A0# etc There are a few in this category... =C2=A0I figure that they are cases of atavistic magic. I bring this up because I find it quite difficult to explain to my students (who are complete newcomers to programming) all the __underscored__ stuff that even rank noobs like them have to deal with. =C2=A0(Trust me, to most of them your reply to my post would be as clear as mud.) Maybe your students do not need to know about it, at least at the beginning ? I heavily use python, and do not use the underscore methods so much most of the time, except for __init__, Believe me, it's not me who's bringing this stuff up: *they* specifically ask. That's precisely my point: it is *they* who somehow feel they can't avoid finding out about this stuff; they must run into such __arcana__ often enough to cause them to wonder. If at least some rank beginners (i.e. some of my students) feel this way, I suggest that some of this alleged __arcana__ should be demoted to a more mundane everyday status, without the scare-underscores. E.g. maybe there should be a built-in is_main(), or some such, so that beginners don't have to venture into the dark underworld of __name__ and __main__. kynn -- http://mail.python.org/mailman/listinfo/python-list
Re: Why all the __double_underscored_vars__?
kj wrote: ... I find it quite difficult to explain to my students (who are complete newcomers to programming) all the __underscored__ stuff that even rank noobs like them have to deal with. =C2=A0(Trust me, to most of them your reply to my post would be as clear as mud.) Believe me, it's not me who's bringing this stuff up: *they* specifically ask. That's precisely my point: it is *they* who somehow feel they can't avoid finding out about this stuff; they must run into such __arcana__ often enough to cause them to wonder. If at least some rank beginners (i.e. some of my students) feel this way, I suggest that some of this alleged __arcana__ should be demoted to a more mundane everyday status, without the scare-underscores. E.g. maybe there should be a built-in is_main(), or some such, so that beginners don't have to venture into the dark underworld of __name__ and __main__. Do you know about Kirby Urner's technique of calling such symbols, ribs, -- the access to the stuff Python is built from? One nice thing about Python is that you can experiment with what these __ribs__ do without having to learn yet another language. It seems nice to me that you can use a rule that says, stick to normal names and you don't have to worry about mucking with the way Python itself works, but if you are curious, looks for those things and fiddle with them. --Scott David Daniels scott.dani...@acm.org -- http://mail.python.org/mailman/listinfo/python-list
Re: Why all the __double_underscored_vars__?
As I understand it, the double underscores is to create a namespace reserved for python's internal use. That way python can add more variables and methods in the future and as long as people respect the namespace their code will not break with future revisions. -- Zachary Burns (407)590-4814 Aim - Zac256FL Production Engineer (Digital Overlord) Zindagi Games -- http://mail.python.org/mailman/listinfo/python-list
Re: Why all the __double_underscored_vars__?
On Fri, Aug 7, 2009 at 5:51 PM, kjno.em...@please.post wrote: Python is chock-full of identifiers beginning and ending with double underscores, such as __builtin__, __contains__, and __coerce__. Using underscores to signal that an identifier is somehow private to an implementation is pretty common in languages other than Python. But in these cases the understanding is that the use of these variables in external code amounts to going behind the API, and is therefore unwise. But as far as I can tell, Python's double-underscore variables are very much part of Python's API. E.g., programmers are specifically instructed to override double-underscore methods to achieve certain functionalities. Right, but the *users* of the functionality provided by __methods__ typically should not invoke such methods directly. For example, one should write `a b`, not `a.__gt__(b)`. The lack of underscores in just plain `gt` would suggest that it's a normal method that could/should be called directly. Also, if the underscore requirement were removed, then people might unknowingly overload an operator without knowing it. The double-underscores indicate that the Python interpreter itself usually is the caller of the method, and as such some level of magic may be associated with it. Other languages have you do the equivalent of `def +():` or `def operator +()` to override an operator, the keyword or symbol serving a similar warning that here be magic. To avoid adding another keyword and the confusion of having punctuation as method names, Python uses a different convention, double leading and trailing underscores. Cheers, Chris -- http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Why all the __double_underscored_vars__?
On Aug 7, 5:13 pm, Chris Rebert c...@rebertia.com wrote: On Fri, Aug 7, 2009 at 5:51 PM, kjno.em...@please.post wrote: Python is chock-full of identifiers beginning and ending with double underscores, such as __builtin__, __contains__, and __coerce__. ...(snip) Right, but the *users* of the functionality provided by __methods__ ...(snip) Cheers, Chris Yes and Python's way is by-far the proper way to handle such functionailty. Don't thank god, thank Guido -- http://mail.python.org/mailman/listinfo/python-list
