docs November 2017

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533 discussions

[issue13047] imp.find_module("") and imp.find_module(".")
by Arfrever Frehtes Taifersar Arahesis 22 Oct '20

22 Oct '20

New submission from Arfrever Frehtes Taifersar Arahesis <Arfrever.FTA(a)GMail.Com>: It's undocumented that imp.find_module("") and imp.find_module(".") try to find __init__.py. There is also a small difference in behavior between them. sys.path by default contains "" as the first element, which is sufficient for imp.find_module("."), but not for imp.find_module(""): $ mkdir /tmp/imp_tests $ cd /tmp/imp_tests $ touch __init__.py $ python3.3 -c 'import imp, sys; print(repr(sys.path[0])); print(imp.find_module("."))' '' (None, '.', ('', '', 5)) $ python3.3 -c 'import imp, sys; print(repr(sys.path[0])); print(imp.find_module(""))' '' Traceback (most recent call last): File "<string>", line 1, in <module> ImportError: No module named '' If sys.path contains path (e.g. "." or absolute path) to directory with __init__.py file, then imp.find_module("") will succeed: $ PYTHONPATH="." python3.3 -c 'import imp, sys; print(repr(sys.path[0:2])); print(imp.find_module("."))' ['', '/tmp/imp_tests'] (None, '.', ('', '', 5)) $ PYTHONPATH="." python3.3 -c 'import imp, sys; print(repr(sys.path[0:2])); print(imp.find_module(""))' ['', '/tmp/imp_tests'] (None, '/tmp/imp_tests/', ('', '', 5)) $ python3.3 -c 'import imp, sys; sys.path.insert(1, "."); print(repr(sys.path[0:2])); print(imp.find_module("."))' ['', '.'] (None, '.', ('', '', 5)) $ python3.3 -c 'import imp, sys; sys.path.insert(1, "."); print(repr(sys.path[0:2])); print(imp.find_module(""))' ['', '.'] (None, './', ('', '', 5)) I think that imp.find_module(".") and imp.find_module("") should have the same behavior, and this behavior should be documented. ---------- assignee: docs@python components: Documentation, Interpreter Core messages: 144531 nosy: Arfrever, docs@python priority: normal severity: normal status: open title: imp.find_module("") and imp.find_module(".") versions: Python 2.7, Python 3.2, Python 3.3 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue13047> _______________________________________

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[issue14979] pdb: Link to source
by anatoly techtonik 22 Oct '20

22 Oct '20

New submission from anatoly techtonik <techtonik(a)gmail.com>: http://docs.python.org/library/pdb.html#pdb.Pdb Documentation for pdb says: "The debugger is extensible — it is actually defined as the class Pdb. This is currently undocumented but easily understood by reading the source." There should a link to the source. ---------- assignee: docs@python components: Documentation, Library (Lib) messages: 162074 nosy: docs@python, techtonik priority: normal severity: normal status: open title: pdb: Link to source _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue14979> _______________________________________

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[issue19438] Where is NoneType in Python 3?
by mpb 21 Oct '20

21 Oct '20

New submission from mpb: types.NoneType seems to have disappeared in Python 3. This is probably intentional, but I cannot figure out how to test if a variable is of type NoneType in Python 3. Specifically, I want to write: assert type (v) in ( bytes, types.NoneType ) Yes, I could write: assert v is None or type (v) is bytes But the first assert statement is easier to read (IMO). Here are links to various Python 3 documentation about None: [1] http://docs.python.org/3/library/stdtypes.html#index-2 [2] http://docs.python.org/3/library/constants.html#None Link [2] says: "None The sole value of the type NoneType." However, NoneType is not listed in the Python 3 documentation index. (As compared with the Python 2 index, where NoneType is listed.) [3] http://docs.python.org/3/library/types.html If NoneType is gone in Python 3, mention of NoneType should probably be removed from link [2]. If NoneType is present in Python 3, the docs (presumably at least one of the above links, and hopefully also the index) should tell me how to use it. Here is another link: [4] http://docs.python.org/3/library/stdtypes.html#bltin-type-objects "The standard module types defines names for all standard built-in types." (Except <class 'NoneType'> ???) None is a built-in constant. It has a type. If None's type is not considered to be a "standard built-in type", then IMO this is surprising(!!) and should be documented somewhere (for example, at link [4], and possibly elsewhere as well.) Thanks! ---------- assignee: docs@python components: Documentation messages: 201666 nosy: docs@python, mpb priority: normal severity: normal status: open title: Where is NoneType in Python 3? versions: Python 3.3 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue19438> _______________________________________

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[issue31432] Documention for CERT_OPTIONAL is misleading
by Christian Heimes 21 Oct '20

21 Oct '20

New submission from Christian Heimes: >From #31431, the documentation of CERT_OPTIONAL and CERT_REQUIRED are misleading. For client side sockets, CERT_OPTIONAL does **NOT** mean that no certificates will be required from the other side of the socket connection. The server **must** provide a cert and the client **requires** the cert to be valid and trusted by trusted CA. Internally, the _ssl.c extension module sets: CERT_NONE: SSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, verify_cb) CERT_OPTIONAL: SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, verify_cb) CERT_REQUIRED: SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT, verify_cb) According to https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_verify.html SSL_VERIFY_FAIL_IF_NO_PEER_CERT is ignored in client mode. This means for client-side sockets: CERT_NONE: server must provide any cert, verification error does not prevent handshake CERT_OPTIONAL == CERT_REQUIRED CERT_REQUIRED: server must provide a correct certificate that is trusted by a root CA in the trust store of the client For server-side sockets: CERT_NONE: Don't ask client for a TLS client auth cert CERT_OPTIONAL: Ask client for a TLS client auth cert, don't fail if the client does not provide one. IIRC the cert must validate and be trusted by a CA in the trust store of the server (TODO: verify this) CERT_REQUIRED: Ask client for TLS client auth cert, fail if client does not provide a certificate during the handshake. ---------- assignee: docs@python components: Documentation, SSL messages: 301970 nosy: christian.heimes, docs@python priority: normal severity: normal status: open title: Documention for CERT_OPTIONAL is misleading type: behavior versions: Python 2.7, Python 3.6, Python 3.7 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue31432> _______________________________________

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[issue30612] Unusual Windows registry path syntax
by Christian Ullrich 20 Oct '20

20 Oct '20

New submission from Christian Ullrich: In 3.6.1, the manual, section 3.1.3, has this to say: "Your administrator will need to activate the “Enable Win32 long paths” group policy, or set the registry value HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem@LongPathsEnabled to 1." Separating a value name from the key path with an @-sign, which is what the above is doing, is something I have never before seen anywhere. I suggest changing it by either: - replacing the instructions for the manual change with a link to <https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).…> or a more suitable reference (I could not find a KB article when I looked) - rewording it as, e.g., ... in the registry key HKEY_...FileSystem, set the REG_DWORD value LongPathsEnabled to 1 The value type could be left out; the value is predefined on all platforms where it will be effective. ---------- assignee: docs@python components: Documentation messages: 295505 nosy: Christian.Ullrich, docs@python priority: normal severity: normal status: open title: Unusual Windows registry path syntax type: enhancement versions: Python 3.6 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue30612> _______________________________________

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[issue29986] Documentation recommends raising TypeError from tp_richcompare
by Devin Jeanpierre 20 Oct '20

20 Oct '20

New submission from Devin Jeanpierre: am not sure when TypeError is the right choice. Definitely, most of the time I've seen it done, it causes trouble, and NotImplemented usually does something better. For example, see the work in https://bugs.python.org/issue8743 to get set to interoperate correctly with other set-like classes --- a problem caused by the use of TypeError instead of returning NotImplemented (e.g. https://hg.python.org/cpython/rev/3615cdb3b86d). This advice seems to conflict with the usual and expected behavior of objects from Python: e.g. object().__lt__(1) returns NotImplemented rather than raising TypeError, despite < not "making sense" for object. Similarly for file objects and other uncomparable classes. Even complex numbers only return NotImplemented! >>> 1j.__lt__(1j) NotImplemented If this note should be kept, this section could use a decent explanation of the difference between "undefined" (should return NotImplemented) and "nonsensical" (should apparently raise TypeError). Perhaps a reference to an example from the stdlib. ---------- assignee: docs@python components: Documentation messages: 291144 nosy: Devin Jeanpierre, docs@python priority: normal pull_requests: 1167 severity: normal status: open title: Documentation recommends raising TypeError from tp_richcompare _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue29986> _______________________________________

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[issue27635] pickle documentation says that unpickling may not call __new__
by July Tikhonov 11 Oct '20

11 Oct '20

New submission from July Tikhonov: A note just below object.__setstate__() documentation https://docs.python.org/3.6/library/pickle.html#object.__setstate__ says that """ … the type should implement __getnewargs__() or __getnewargs_ex__() to establish such an invariant; otherwise, neither __new__() nor __init__() will be called. """ I believe that note about not calling __new__() was relevant in python2. I could not find case in python3 in which __new__() would not be called. And __init__() is not called anyway, as far as I understand (unless explicitly by __setstate__() or something). Python 3.6.0a3+ (default:da9898e7e90d, Jul 27 2016, 19:51:12) [GCC 4.9.3] on linux Type "help", "copyright", "credits" or "license" for more information. >>> class C: ... def __getstate__(self): return {'foo' : self.foo} ... def __setstate__(self, state): self.foo = state['foo'] ... def __new__(cls): ... print('__new__ is called'); return super().__new__(cls) ... def __init__(self): ... print('__init__ is called'); self.foo = None; super().__init__() ... >>> c = C(); c.foo = 'bar' __new__ is called __init__ is called >>> import pickle >>> c2 = pickle.loads(pickle.dumps(c)) __new__ is called >>> c2.foo 'bar' ---------- assignee: docs@python components: Documentation messages: 271465 nosy: docs@python, july priority: normal severity: normal status: open title: pickle documentation says that unpickling may not call __new__ versions: Python 3.4, Python 3.5, Python 3.6 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue27635> _______________________________________

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[issue26964] Incorrect documentation for `-u`-flag
by Olav Morken 11 Oct '20

11 Oct '20

New submission from Olav Morken: The documentation for the `-u`-flag (https://docs.python.org/3/using/cmdline.html#cmdoption-u) contains: > The text I/O layer will still be line-buffered if writing to the console, or block-buffered if redirected to a non-interactive file. This does not appear to be the case -- instead it is always line-buffered: https://hg.python.org/cpython/file/v3.5.1/Python/pylifecycle.c#l1041 Attached is a trivial patch that simply removes everything after "line-buffered". ---------- assignee: docs@python components: Documentation files: fix-doc-unbuffered.patch keywords: patch messages: 264910 nosy: docs@python, olavmrk priority: normal severity: normal status: open title: Incorrect documentation for `-u`-flag Added file: http://bugs.python.org/file42736/fix-doc-unbuffered.patch _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue26964> _______________________________________

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[issue23984] Documentation error: Descriptors
by bjonnh 09 Oct '20

09 Oct '20

New submission from bjonnh: in https://docs.python.org/3.5/howto/descriptor.html#static-methods-and-class-… (same problem in all python 3.x documentations) There is this example where the return of f function is printed and there is already a print in the function: """ >>> class E(object): def f(x): print(x) f = staticmethod(f) >>> print(E.f(3)) 3 >>> print(E().f(3)) 3 """ It should probably be: """ def f(x): return(x) """ or """ >> E.f(3) 3 >> E().f(3) """ ---------- assignee: docs@python components: Documentation messages: 241312 nosy: bjonnh, docs@python priority: normal severity: normal status: open title: Documentation error: Descriptors type: enhancement versions: Python 3.2, Python 3.3, Python 3.4, Python 3.5, Python 3.6 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue23984> _______________________________________

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[issue30578] Misleading example in sys.set_coroutine_wrapper docs
by Nick Coghlan 05 Oct '20

05 Oct '20

New submission from Nick Coghlan: In issue 24342, the invocation of coroutine wrappers specified via sys.set_coroutine_wrapper was fixed to catch and report the case of infinite recursion, where the wrapper attempts to instantiate a nested coroutine (which would call the wrapper, which would attempt to instantiate the coroutine, etc, etc) The docs for sys.set_coroutine_wrapper include an example of this failure case: https://docs.python.org/3/library/sys.html#sys.set_coroutine_wrapper However, if you're not reading carefully, it looks like an example of how to *use* sys.set_coroutine_wrapper, rather than an example of a case that won't work. It would be better to include an example that either doesn't wrap the coroutine at all, or else uses one of the non-native coroutine emulations to avoid the infinite recursion problem: ``` import asyncio, sys def wrapper(coro): @asyncio.coroutine def wrap(coro): print("Coroutine started") result = yield from coro print("Coroutine finished") return result return wrap(coro) sys.set_coroutine_wrapper(wrapper) async def foo(): print("Coroutine running") return "Coroutine result" import asyncio asyncio.get_event_loop().run_until_complete(foo()) ``` Also related: I discovered in writing this that "sys.set_coroutine_wrapper(None)" doesn't actually turn off coroutine wrapping. Instead, you still get this exception when attempting to recursively define an unwrapped one: RuntimeError: coroutine wrapper <NULL> attempted to recursively wrap <code object wrap at 0x7eff31fbde40, file "<stdin>", line 2>) That error was produced as follows: ``` import sys, contextlib @contextlib.contextmanager def disable_coroutine_wrapping(): wrapper = sys.get_coroutine_wrapper() sys.set_coroutine_wrapper(None) try: yield finally: sys.set_coroutine_wrapper(wrapper) def wrapper(coro): async def wrap(coro): print("Coroutine started") result = await coro print("Coroutine finished") return result with disable_coroutine_wrapping(): return wrap(coro) sys.set_coroutine_wrapper(wrapper) async def foo(): print("Coroutine running") return "Coroutine result" import asyncio asyncio.get_event_loop().run_until_complete(foo()) ``` ---------- assignee: docs@python components: Documentation messages: 295231 nosy: docs@python, giampaolo.rodola, haypo, ncoghlan, yselivanov priority: normal severity: normal stage: needs patch status: open title: Misleading example in sys.set_coroutine_wrapper docs type: enhancement versions: Python 3.6, Python 3.7 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue30578> _______________________________________

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docs November 2017