Mailman 3 January 2020 - docs

Small error in the Python tutorial section 3.2
by Mateus Souza 26 Jan '20

26 Jan '20

The error is here https://docs.python.org/3/tutorial/introduction.html, in the 3.2 section. The Fibonacci code has a mistake, it doesn't actually return the sequence 0,1,1,2,3,5,8 it is returning 0,1,2,4,8 I made it return the correct sequence by doing a,b,temp = 0,1,0 while (a < 90): print(a) temp=a a=b b=temp+b Keep in mind that I'm new to programming, so maybe it could be done better than this.

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[issue39374] Key in sort -> Callable Object instead of function
by Carlos Segura González 26 Jan '20

26 Jan '20

New submission from Carlos Segura González <carlos.segura(a)cimat.mx>: In the Documentation, the "Sorting HOW TO" (https://docs.python.org/3/howto/sorting.html) states that "have a key parameter to specify a function to be called". However, it might be other callable objects. In fact, some of the examples given in the documentation are not with functions. I suggest: "have a key parameter to specify a callable object that is called..." ---------- assignee: docs@python components: Documentation messages: 360219 nosy: Carlos Segura González, docs@python priority: normal severity: normal status: open title: Key in sort -> Callable Object instead of function versions: Python 3.5, Python 3.6, Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue39374> _______________________________________

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[issue39446] Documentation should reflect that all dicts are now ordered
by Michael Shields 26 Jan '20

26 Jan '20

New submission from Michael Shields <michael.shields(a)freenome.com>: As of Python 3.7, dicts always preserve insertion order. This is mentioned briefly in the release notes, but it would also be helpful to mention it in the language reference, and in the discussion of collections.OrderedDict. ---------- assignee: docs@python components: Documentation messages: 360642 nosy: Michael Shields, docs@python priority: normal severity: normal status: open title: Documentation should reflect that all dicts are now ordered versions: Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue39446> _______________________________________

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[issue39234] `enum.auto()` incrementation value not specified.
by YoSTEALTH 26 Jan '20

26 Jan '20

New submission from YoSTEALTH <ritesh(a)stealthcentral.com>: # enum in C # --------- enum { a, b, c } # a = 0 # b = 1 # b = 2 # enum in Python # -------------- class Count(enum.IntEnum): a = enum.auto() b = enum.auto() c = enum.auto() # a = 1 # b = 2 # b = 3 I am not sure why the `enum.auto()` starts with 1 in Python but this has just wasted a week worth of my time. ---------- assignee: docs@python components: Documentation messages: 359452 nosy: YoSTEALTH, docs@python priority: normal severity: normal status: open title: `enum.auto()` incrementation value not specified. versions: Python 3.6, Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue39234> _______________________________________

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[issue36654] Add example to tokenize.tokenize
by Windson Yang 26 Jan '20

26 Jan '20

New submission from Windson Yang <wiwindson(a)outlook.com>: > The tokenize() generator requires one argument, readline, which must be a callable object which provides the same interface as the io.IOBase.readline() method of file objects. Each call to the function should return one line of input as bytes. Add an example like this should be easier to understand: # example.py def foo: pass # tokenize_example.py import tokenize f = open('example.py', 'rb') token_gen = tokenize.tokenize(f.readline) for token in token_gen: # Something like this # TokenInfo(type=1 (NAME), string='class', start=(1, 0), end=(1, 5), line='class Foo:\n') # TokenInfo(type=1 (NAME), string='Foo', start=(1, 6), end=(1, 9), line='class Foo:\n') # TokenInfo(type=53 (OP), string=':', start=(1, 9), end=(1, 10), line='class Foo:\n') print(token) ---------- assignee: docs@python components: Documentation messages: 340467 nosy: Windson Yang, docs@python priority: normal severity: normal status: open title: Add example to tokenize.tokenize type: enhancement versions: Python 3.5, Python 3.6, Python 3.7, Python 3.8 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue36654> _______________________________________

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[issue15243] Misleading documentation for __prepare__
by William Schwartz 26 Jan '20

26 Jan '20

New submission from William Schwartz <wkschwartz(a)gmail.com>: Section 3.3.3.2. "Preparing the class namespace" of the documentation (http://docs.python.org/dev/reference/datamodel.html#preparing-the-class-nam…) states that "If the metaclass has a __prepare__ attribute, it is called as ``namespace = metaclass.__prepare__(name, bases, **kwds)``...." This isn't quite true. By just defining a ``__prepare__`` method in a metaclass, the interpreter calls it as it would a static method -- there is no implicit first argument referring to ``metaclass`` as the documentation implies. The documentation should be amended to say that users can decorate ``__prepare__`` as a class method to get ``metaclass`` passed in as the implicit first argument. ---------- assignee: docs@python components: Documentation, Tests messages: 164606 nosy: William.Schwartz, docs@python priority: normal severity: normal status: open title: Misleading documentation for __prepare__ type: behavior versions: Python 3.3 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue15243> _______________________________________

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[issue37955] mock.patch incorrect reference to Mock
by Paulo Henrique Silva 25 Jan '20

25 Jan '20

New submission from Paulo Henrique Silva <ph.silva(a)gmail.com>: When explaining the usage of keyword arguments on mock.patch: ``` patch() takes arbitrary keyword arguments. These will be passed to the Mock (or new_callable) on construction. ``` default new_callable is MagicMock and it should be mentioned here instead of Mock (even tough MagickMock inherits from it). ---------- assignee: docs@python components: Documentation messages: 350537 nosy: docs@python, phsilva priority: normal severity: normal status: open title: mock.patch incorrect reference to Mock versions: Python 3.9 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue37955> _______________________________________

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[issue39444] Incorrect description of sorting for PrettyPrinter
by Steven DeRose 25 Jan '20

25 Jan '20

New submission from Steven DeRose <sderose(a)acm.org>: The doc for pprint.PrettyPrinter at https://docs.python.org/3/library/pprint.html says: If sort_dicts is true (the default), dictionaries will be formatted with their keys sorted, otherwise they will display in insertion order I believe the insertion order is not even known by normal dicts (only by OrderedDict), so I think the last phrase must be wrong. If it's somehow correct, it deserves explaining.... ---------- assignee: docs@python components: Documentation messages: 360630 nosy: TextGeek, docs@python priority: normal severity: normal status: open title: Incorrect description of sorting for PrettyPrinter versions: Python 3.8 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue39444> _______________________________________

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[issue11553] Docs for: import, packages, site.py, .pth files
by Graham Wideman 25 Jan '20

25 Jan '20

New submission from Graham Wideman <initcontact(a)grahamwideman.com>: The overall scope of this issue is that current Python documentation gives vague, sometimes incorrect, information about the set of Python features involved in modularizing functionality. This issue presents an obstacle to programmers making smooth transitions from a single module, to collections of modules and packages, then on to neatly organized common packages shared between projects. The problem affects documentation of: import and from...import statements ------------------------------------ The Language Reference is way too complicated for the mainstream case. Exactly what variants of arguments are possible, and what are their effects? What are the interactions with package features, such as whether or not modules have been explicitly imported into package __init_.py? sys.path --------- Typical consituents; range of alternatives for adding more dirs Module site.py -------------- Multiple serious errors in the file docstring, relating to site-packages directories and .pth files .pth files ----------- Incorrectly described in site.py, and then vaguely described in other docs. Are .pth files processed everywhere on sys.path? Can they be interative? (No to both). package structure ----------------- Details of package structure have evidently changed over Python versions. Current docs are unclear on points such as: -- is __init__.py needed on subpackage directories? -- the __all__ variable: Does it act generally to limit visibility of a module or package's attributes, or does pertain only to the 'from...import *' statement? Details: ========= Language Reference ------------------- http://docs.python.org/py3k/reference/simple_stmts.html#the-import-statement The description of the import statement is extensive, but dauntingly complicated for the reader trying to understand the mainstream case of simply importing modules or packages that are on sys.path. This is because the algorithm for finding modules tries numerous esoteric strategies before falling back on the plain-old-file-system method. (Even now that I have a good understanding of the plain-old-file variations of import, I reread this and find it hard to comprehend, and disorganized and incomplete in presenting the available variations of the statement.) Grammar issue: the grammar shown for the import statement shows: relative_module ::= "."* module | "."+ ... which implies that relative module could have zero leading dots. I believe an actual relative path is required to have at least one dot (PEP 328). Evidently, in this grammar, 'relative_module' really means "relative or absolute path to module or package", so it would be quite helpful to change to: relative_path ::= "."+ module | "."+ from_path ::= (relative_path | module) etc. (Really 'module' is not quite right here either since it's used to mean module-or-package.) site.py: -------- Module site.py implements the site-package related features. The docstring has multiple problems with consequences in other docs. 1. Does not mention user-specific site-package directories (implemented by addusersitepackages() ) 2. Seriously misleading discussion of .pth files. In the docstring the example shows using pth files, called "package configuration files" in their comments, to point to actual package directories bar and foo located within the site-packages directory. This is an absolutely incorrect use of pth files: If foo and bar are packages in .../site-packages/, they do not need to be pointed to, they are already on sys.path. If the package dirs ARE pointed to by foo.pth and bar.pth, the modules inside them will be exposed directly to sys.path, possibly precipitating name collisions. Further, programmers following this example will create packages in which import statements will appear to magically perform relative imports without leading dots, leading to confusion over how the import statement is supposed to work. It may be that this discussion is held over from a time when "package" perhaps meant "Just a Bunch of Files in a Directory"? 3. The docstring (or other docs) should make clear that .pth files are ONLY processed within site-package directories (ie: only by site.py). 4. Bug: Minor: In addsitepackages(), the library directory for Windows (the else clause) is shown as lower-case 'lib' instead of 'Lib'. This has some possibility of causing problems when running from a case-sensitive server. In any case, if read as documentation it is misleading. Tutorial --------- 6. Modules: http://docs.python.org/py3k/tutorial/modules.html 1. Discussion (6.1.2. The Module Search Path) is good as far as it goes, but it doesn't mention the site-package directories. 2. Section 6.4. Packages: Discussion of __init__.py does describe the purpose of these files. However, the discussion in relation to subpackages should mention that for subdirectories to be accessible they must in fact be made into subpackages. I.e.: there is not form of import that can reach into a subdir of a package *unless* it's flagged as a subpackage using __init__.py. I have read elsewhere that there were some versions of Python where __init__.py was not needed on subdirs within a package. 3. Section 6.4. Packages: The discussion of __all__ should note that it works *only* in conjunction with 'from...import *', and is not a general mechanism for limiting visibility of attributes. Attributes not in the __all__ list are still accessible using other forms of import. 4. Section 6.4. Packages: "Note that when using from package import item" and following. Draws a contrast between: from package import item vs import item.subitem.subsubitem However, this muddles the roles of the arguments to import, and notably uses 'item' in two different ways. Instead the discussion can be presented as a comparison of: from PackageOrModule import ModuleOrAttribute vs import PackageOrModule ... where it can be pointed out that the PackageOrModule 'dotted path' argument follows the *same* rules in both cases (except for relative paths). The *salient* contrast is that only the 'from' form has a *second* argument which can be an attribute. 5. Footnote: (somewhat unrelated, but...) says "the execution of a module-level function enters the function name in the module’s global symbol table." This is surely incorrect -- it is the execution of the function's *def* that enters the function name in the symbol table. Standard Library Reference --------------------------- 1) 27.13. site — Site-specific configuration hook http://docs.python.org/py3k/library/site.html This is documentation for site.py, and is a page that might well come up in a search for '.pth'. 1a) This page may simply be importing the docstring from site.py? In any case it repeats the ommissions and errors noted above for site.py. 2) 27.1. sys — System-specific parameters and functions http://docs.python.org/py3k/library/sys.html Documentation for sys.path. OK as far as it goes, but: 2a) Could helpfully point to a discussion of the typical items to be found in sys.path under normal circumstances 2b) It does point to the site.py module documentation as the authoritative info on using .pth files (which is seriously flawed as noted above). 3) 29.3. pkgutil — Package extension utility. http://docs.python.org/py3k/library/pkgutil.html 3a) The info for pkgutil.extend_path() describes how .pkg files are similar to .pth files, and their entries should point to package directories. As I noted above, so far as I can see, package directories should be within a directory on sys,path, but should not themselves be included in the path, otherwise it breaks their capability to work properly as packages. 'Installing Python Modules' document: -------------------------------------- http://docs.python.org/py3k/install/index.html This may well be consulted for info on how to organize source files, though it is basically the doc for Distutils. 1. Main problem is that it seems quite out-of-date; "Windows has no concept of a user’s home directory, " and so on. 2. 'How installation works' > table. For Windows suggests 'prefix' (default: C:\Python) as an installation directory. This is indeed one of the possible 'site-package' directories, but surely it is deprecated in favor of C:\Python\Lib\site-packages, which this section does not mention. 3. Does not mention user-specific site-package directories. 4. 'Modifying Python's Search Path' > "The most convenient way is to add a path configuration file to a directory that’s already on Python’s path". This is incorrect. (a) .pth files are only processed in site-package directories. (b) Clarifying an additional point of confusion -- as a consequence of (a) .pth files cannot be chained. 5. Points to docs for site.py... with it's flaws noted above. PEP 302 New Import Hooks ------------------------ Given the vagueness elsewhere in the docs, one might go hunting for ground truth in the PEPs. One must allow for PEPs having been superceeded, but nonetheless, outdated info that is now wrong is an additional stumbling block for learners. 1. Section 'Specification part 1: The importer Protocol'. Discussion says that in an import statement, a path (with no leading '.') is first treated as relative. This is now incorrect (as spelled out in PEP 328.) It would be helpful to insert a note in PEP 302 pointing out that the later revision invalidates this passage. ---------- assignee: docs@python components: Documentation messages: 130964 nosy: docs@python, gwideman priority: normal severity: normal status: open title: Docs for: import, packages, site.py, .pth files type: behavior versions: Python 3.1, Python 3.2, Python 3.3 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue11553> _______________________________________

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[issue39392] Python Turtle is not filling alternate overlapping areas of a shape with same color
by Terry J. Reedy 25 Jan '20

25 Jan '20

Terry J. Reedy <tjreedy(a)udel.edu> added the comment: Your SO question is essentially a duplicate. As I answered there, the graphics systems of Unix and Windows, used by tk and hence tkinter, handle filling of self-intersecting polygons differently. On Windows, if one draws a line from the outside to a particular region without going through an intersection, each line crossing toggles 'fill', starting with 'off' in the outside. The rule seems to be reversed for overlapping items, such as circles. On Windows, all three circles are yellow, whereas on macOS, the 60 circle is white, even if drawn last! So, no bug. The best we can do is document 'filling' for turtle. Our tkinter doc does not include tk widgets, in particular Canvas, and we cannot edit external sources. What happens with multiple fill colors? Blended, or last wins? # 1 fill block from turtle import * color('black', 'yellow') begin_fill() circle(40) color('black', 'red') circle(60) color('black', 'blue') circle(80) end_fill() On Windows, 3 circles drawn, then all filled with blue. The same is true if the circle order is reversed. # multiple fill blocks from turtle import * color('black', 'yellow') begin_fill() circle(40) end_fill() color('black', 'red') begin_fill() circle(60) end_fill() color('black', 'blue') begin_fill() circle(80) end_fill() On Windows, each circle fills with its color after it is drawn. Same final result. It is different if drawing order is reversed. The rule seems to be: lines are drawn with the current line color; fill is done at the end of each fill block with the current (last) fill color. ---------- assignee: -> docs@python components: +Documentation -Tkinter nosy: +docs@python, terry.reedy stage: -> needs patch type: behavior -> versions: +Python 3.8, Python 3.9 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue39392> _______________________________________

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