[issue11318] Python 3.2 FAQ example code typo?
Boštjan Mejak bostjan.me...@gmail.com added the comment: Understood. Now I get it. If you create an instance c of the class C (so c = C() ) and try to get the variable count from that class, then c.count is the same reference as C.count. Please make that clearer in the FAQ by saying If you create an instance c of the class C, then c.count is the same reference as C.count. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
New submission from Boštjan Mejak bostjan.me...@gmail.com: I have found a possible typo in an example code of Python 3.2. It's located on page 32 in the PDF version of the FAQ document. The code is: class C: count = 0 # number of times C.__init__ called def __init__(self): C.count = C.count + 1 def getcount(self): return C.count # or return self.count The code block of the __init__ method is the thing that has the typo. Shouldn't C.count = C.count + 1 be c.count = C.count + 1 ? Because the text after this code example says: c.count also refers to C.count for any c such that isinstance(c, C) holds /.../. How can c.count also refer to C.count if there is no c.count in the present code example in the FAQ of Python 3.2? If this is a typo, please fix it for Python 3.2 and also for other Python versions with the same typo. Else if this is not a typo, explain how can c.count refer to C.count if there is no c.count in the code example. -- assignee: docs@python components: Documentation messages: 129357 nosy: Retro, docs@python priority: normal severity: normal status: open title: Python 3.2 FAQ example code typo? versions: Python 3.2 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
R. David Murray rdmur...@bitdance.com added the comment: Read a little further: Caution: within a method of C, an assignment like ``self.count = 42`` creates a new and unrelated instance named count in ``self``'s own dict. That is, c.count refers to C.count right up until the point where c.count is assigned a value. So, c.count = c.count + 1 will add one to the current value of C.count, and assign it to the *instance* variable c.count. c.count at that point no longer refers to the *class* variable C.count. Thus your change to the __init__ function would completely defeat the purpose of the example (which is to show how to use a *class* variable. If you can suggest a concise wording that would have made this clearer to you, we can consider a doc patch. -- nosy: +r.david.murray type: - behavior ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
R. David Murray rdmur...@bitdance.com added the comment: Hmm. Rereading your message, is seems like you just didn't understand the statement c.count refers to C.count for any That is a statement about how the language behaves. If there is not yet an instance variable 'count', but a class variable 'count' exists, then the value of the class variable is used when c.count is evaluated. A class is a two level nested name space with a couple of special properties. I don't really see any way to make that statement clearer. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Boštjan Mejak bostjan.me...@gmail.com added the comment: Caution: within a method of C, an assignment like ``self.count = 42`` creates a new and unrelated instance named count in ``self``'s own dict. More clear is to say *Caution: within a method of class C, an assignment like ``self.count = 42`` creates a new and unrelated instance named count in ``self``'s own dict.* * * -- Added file: http://bugs.python.org/file20888/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___blockquote class=gmail_quote style=margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex; span class=Apple-style-span style=border-collapse: collapse; color: rgb(32, 32, 32); font-family: #39;Droid Sans#39;, arial, sans-serif; font-size: 13px; Caution: within a method of C, an assignment like ``self.count = 42`` creates a new and unrelated instance named quot;countquot; in ``self``#39;s own dict./span/blockquote divbr/divdivMore clear is to say span class=Apple-style-span style=border-collapse: collapse; color: rgb(32, 32, 32); font-family: #39;Droid Sans#39;, arial, sans-serif; font-size: 13px; iCaution: within a method of class C, an assignment like ``self.count = 42`` creates a new and unrelated instance named quot;countquot; in ``self``#39;s own dict./i/span/div divspan class=Apple-style-span style=border-collapse: collapse; color: rgb(32, 32, 32); font-family: #39;Droid Sans#39;, arial, sans-serif; font-size: 13px; ibr/i/span/div ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Boštjan Mejak bostjan.me...@gmail.com added the comment: So you're saying that if a class' name is C, then c.count is the same as C.count? I thought Python is case-sensitive. You know: c (small letter c) is not equal to C (big letter C) in Python. I don't understand what you mean by c.count because my intepreter always throws an exception that c is not defined if I feed it with this code example and doc.count -- Added file: http://bugs.python.org/file20890/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___So you#39;re saying that if a class#39; name is C, then c.count is the same as C.count? I thought Python is case-sensitive. You know: c (small letter c) is not equal to C (big letter C) in Python. I don#39;t understand what you mean by c.count because my intepreter always throws an exception that c is not defined if I feed it with this code example and do  gt;gt;gt; c.count ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Georg Brandl ge...@python.org added the comment: Now it's clear that David is right -- what c refers to is defined in this very sentence. -- nosy: +georg.brandl resolution: - invalid status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Boštjan Mejak bostjan.me...@gmail.com added the comment: I don't understand it. My bad. Please explain to me exactly what c refers to. -- Added file: http://bugs.python.org/file20891/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___I don#39;t understand it. My bad. Please explain to me exactly what quot;cquot; refers to. ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
R. David Murray rdmur...@bitdance.com added the comment: Please consult the python tutor's list, the bug tracker is not the place to get introductory help with Python. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Boštjan Mejak bostjan.me...@gmail.com added the comment: How awful! A little pointer to the tutorial where this is explained would be also quite smashing. -- Added file: http://bugs.python.org/file20893/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___How awful! A little pointer to the tutorial where this is explained would be also quite smashing. ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Boštjan Mejak bostjan.me...@gmail.com added the comment: c.count also refers to C.count Where in the code is c.count? Please explain this for the sake of really closing this issue. -- Added file: http://bugs.python.org/file20896/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___quot;span class=Apple-style-span style=border-collapse: collapse; color: rgb(32, 32, 32); font-family: #39;Droid Sans#39;, arial, sans-serif; font-size: 13px; c.count also refers to C.countquot;  Where in the code is quot;c.countquot;? Please explain this for the sake of really closing this issue./span ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Changes by Éric Araujo mer...@netwok.org: Removed file: http://bugs.python.org/file20888/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Changes by Éric Araujo mer...@netwok.org: Removed file: http://bugs.python.org/file20890/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Changes by Éric Araujo mer...@netwok.org: Removed file: http://bugs.python.org/file20891/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Changes by Éric Araujo mer...@netwok.org: Removed file: http://bugs.python.org/file20893/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Changes by Éric Araujo mer...@netwok.org: Removed file: http://bugs.python.org/file20896/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Éric Araujo mer...@netwok.org added the comment: If the tutorial is not clear enough, try for example http://diveintopython.org/object_oriented_framework/class_attributes.html. Please ask on a suitable venue if you don’t understand instead of this tracker. (Please don’t send HTML email to this tracker, it creates false attachments.) -- nosy: +eric.araujo ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Boštjan Mejak bostjan.me...@gmail.com added the comment: Eric, the thing I don't understand is why is there that c.count thing. How is it possible for c.count to be the same reference as C.count? Where is c defined? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Éric Araujo mer...@netwok.org added the comment: What this part means is: “If you create an instance of C named c, and get c.count, it will get the attribute count defined on C.” IOW: You can get a class variable from any instance. In the example, the code in __init__ cannot assign to self.count, because it wants to increment the attribute on the class, not on the instance. This is very well explained in Dive Into Python. Please experiment in a shell and ask on appropriate venues after this message. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11318] Python 3.2 FAQ example code typo?
Changes by Éric Araujo mer...@netwok.org: -- assignee: docs@python - nosy: -docs@python, eric.araujo ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11318 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
