Mailman 3 September 2017 - Python-ideas

allow overriding files used for the input builtin
by Wren Turkal Sept. 29, 2017

Sept. 29, 2017

Hi there, I have posted an idea for improvement with a PR of an implementation to https://bugs.python.org/issue31603. The basic idea is to add fin, fout, and ferr file object parameters and default to using what is used today when the args are not specified. I believe this would be useful to allow captures input and send output to specific files when using input. The input builtin has some logic to use readline if it's available. It would be nice to be able to use this same logic no matter … [View More]

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Re: [Python-ideas] allow overriding files used for the input builtin
by Adam Bartoš Sept. 29, 2017

Sept. 29, 2017

Hello, it seems that there are two independent issues – a way to temporarily replace all sys.std* streams, and a way to use the special interactive readline logic for arbitrary terminal-like file. I thought that OP's concern was the latter. In that case shouldn't there just be a way to produce an IO object f whose .readline() (or other special method) does this and has an optional prompt argument? The OP's code would become with open_terminal('/dev/tty') as f: name = f.readline(prompt='… [View More]

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Fwd: A PEP to define basical metric which allows to guarantee minimal code quality
by Pavol Lisy Sept. 25, 2017

Sept. 25, 2017

On 9/20/17, alexandre.galode(a)gmail.com <alexandre.galode(a)gmail.com> wrote: [...] > But i think, as wee need to avoid to talk about any tool name in the PEP, > we need to avoid to give a code example. The aim of this proposal is to > have a guideline on minimal metrics to have minimal quality. Michel Foucault wrote book (https://en.wikipedia.org/wiki/The_Birth_of_the_Clinic) which subtitle is "An Archaeology of Medical Perception". Imagine that code is organism and quality … [View More]

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Hexadecimal floating literals
by Serhiy Storchaka Sept. 24, 2017

Sept. 24, 2017

The support of hexadecimal floating literals (like 0xC.68p+2) is included in just released C++17 standard. Seems this becomes a mainstream. In Python float.hex() returns hexadecimal string representation. Is it a time to add more support of hexadecimal floating literals? Accept them in float constructor and in Python parser? And maybe add support of hexadecimal formatting ('%x' and '{:x}')?

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A PEP to define basical metric which allows to guarantee minimal code quality
by Alexandre GALODE Sept. 21, 2017

Sept. 21, 2017

Hi everybody, I'm a Python dev since about 10 years. I saw that customers are more and more curious about development process, talking from various reference on which allow to define what they call "good quality code". Someones are talking only about Pylint, other one from SonarQube, ... I search for SonarQube for Python, and saw it was using Pylint, coverage and Unittest. I saw also some customers internal tools which, every of them, was using internal tool, pylint, pylama, pep8, ... … [View More]

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Move some regrtest or test.support features into unittest?
by Victor Stinner Sept. 19, 2017

Sept. 19, 2017

Hi, tl; dr How can we extend unittest module to plug new checks before/after running tests? The CPython project has a big test suite in the Lib/test/ directory. While all tests are written with the unittest module and the unittest.TestCase class, tests are not run directly by unittest, but run by "regrtest" (for "regression test") which is a test runner doing more checks (and more). I would like to see if and how we can integrate/move some regrtest features into the unittest module. … [View More]Example of regrtest features: * skip a test if it allocates too much memory, command line argument to specify how many memory a test is allowed to allocate (ex: --memlimit=2G for 2 GB of memory) * concept of "resource" like "network" (connect to external network servers, to the Internet), "cpu" (CPU intensive tests), etc. Tests are skipped by default and enabled by the -u command line option (ex: "-u cpu). * track memory leaks: check the reference counter, check the number of allocated memory blocks, check the number of open file descriptors. * detect if the test spawned a thread or process and the thread/process is still running at the test exit * --timeout: watchdog killing the test if the run time exceed the timeout in seconds (use faulthandler.dump_traceback_later) * multiprocessing: run tests in subprocesses, in parallel * redirect stdout/stderr to pipes (StringIO objects), ignore them on success, or dump them to stdout/stderr on test failure * --slowest: top 10 of the slowest tests * --randomize: randomize test order * --match, --matchfile, -x: filter tests * --forever: run the test in a loop until it fails (or is interrupted by CTRL+c) * --list-tests / --list-cases: list test files / test methods * --fail-env-changed: mark tests as failed if a test altered the environment * detect if a "global variable" of the standard library was modified but not restored by the test: resources = ('sys.argv', 'cwd', 'sys.stdin', 'sys.stdout', 'sys.stderr', 'os.environ', 'sys.path', 'sys.path_hooks', '__import__', 'warnings.filters', 'asyncore.socket_map', 'logging._handlers', 'logging._handlerList', 'sys.gettrace', 'sys.warnoptions', 'multiprocessing.process._dangling', 'threading._dangling', 'sysconfig._CONFIG_VARS', 'sysconfig._INSTALL_SCHEMES', 'files', 'locale', 'warnings.showwarning', 'shutil_archive_formats', 'shutil_unpack_formats', ) * test.bisect: bisection to identify the failing method, used to track memory leaks or identify a test leaking a resource (ex: create a file but don't remove it) * ... : regrtest has many many features My question is also connected to test.support (Lib/test/support/__init__.py): a big module containing a lot of helper functions to write tests and to detect bugs in tests. For example, @reap_children decorator emits a warnig if the test leaks a child process (and reads its exit status to prevent zombie process). I started to duplicate code in many files of Lib/test/test_*.py to check if tests "leak running threads" ("dangling threads"). Example from Lib/test/test_theading.py: class BaseTestCase(unittest.TestCase): def setUp(self): self._threads = test.support.threading_setup() def tearDown(self): test.support.threading_cleanup(*self._threads) test.support.reap_children() I would like to get this test "for free" directly from the regular unittest.TestCase class, but I don't know how to extend the unittest module for that? Victor [View Less]

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Use __all__ for dir(module) (Was: PEP 562)
by Cody Piersall Sept. 18, 2017

Sept. 18, 2017

On Tue, Sep 12, 2017 at 3:26 AM, Ivan Levkivskyi <levkivskyi(a)gmail.com> wrote: > @Cody >> I still think the better way >> to solve the custom dir() would be to change the module __dir__ >> method to check if __all__ is defined and use it to generate the >> result if it exists. This seems like a logical enhancement to me, >> and I'm planning on writing a patch to implement this. Whether it >> would be accepted is still an open issue though. > &… [View More]

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Make map() better
by Jason H Sept. 17, 2017

Sept. 17, 2017

The format of map seems off. Coming from JS, all the functions come second. I think this approach is superior. Currently: map(lambda x: chr(ord('a')+x), range(26)) # ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'] But I think this reads better: map(range(26), lambda x: chr(ord('a')+x)) Currently that results in: TypeError: argument 2 to map() must support iteration Also, how are we to tell what supports map()?… [View More]

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sys.py
by Eric Snow Sept. 14, 2017

Sept. 14, 2017

The sys module is a rather special case as far as modules go. It is effectively a "console" into the interpreter's internal state and that includes some mutable state. Since it is a module, we don't have much of an opportunity to: * validate values assigned to its attributes [1] * issue DeprecationWarning for deprecated attrs [2] * alias attrs [2] * replace get (and get/set) functions with properties * re-organize sys [3] One possible solution I've been toying with for quite a while [2] is … [View More]

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PEP 554: Stdlib Module to Support Multiple Interpreters in Python Code
by Eric Snow Sept. 14, 2017

Sept. 14, 2017

Hi all, As part of the multi-core work I'm proposing the addition of the "interpreters" module to the stdlib. This will expose the existing subinterpreters C-API to Python code. I've purposefully kept the API simple. Please let me know what you think. -eric https://www.python.org/dev/peps/pep-0554/ https://github.com/python/peps/blob/master/pep-0554.rst https://github.com/python/cpython/pull/1748 https://github.com/python/cpython/pull/1802 https://github.com/ericsnowcurrently/cpython/… [View More]tree/high-level-interpreters-m… ********************************************** PEP: 554 Title: Multiple Interpreters in the Stdlib Author: Eric Snow <ericsnowcurrently(a)gmail.com> Status: Draft Type: Standards Track Content-Type: text/x-rst Created: 2017-09-05 Python-Version: 3.7 Post-History: Abstract ======== This proposal introduces the stdlib "interpreters" module. It exposes the basic functionality of subinterpreters that exists in the C-API. Rationale ========= Running code in multiple interpreters provides a useful level of isolation within the same process. This can be leveraged in number of ways. Furthermore, subinterpreters provide a well-defined framework in which such isolation may extended. CPython has supported subinterpreters, with increasing levels of support, since version 1.5. While the feature has the potential to be a powerful tool, subinterpreters have suffered from neglect because they are not available directly from Python. Exposing the existing functionality in the stdlib will help reverse the situation. Proposal ======== The "interpreters" module will be added to the stdlib. It will provide a high-level interface to subinterpreters and wrap the low-level "_interpreters" module. The proposed API is inspired by the threading module. The module provides the following functions: enumerate(): Return a list of all existing interpreters. get_current(): Return the currently running interpreter. get_main(): Return the main interpreter. create(): Initialize a new Python interpreter and return it. The interpreter will be created in the current thread and will remain idle until something is run in it. The module also provides the following class: Interpreter(id): id: The interpreter's ID (read-only). is_running(): Return whether or not the interpreter is currently running. destroy(): Finalize and destroy the interpreter. run(code): Run the provided Python code in the interpreter, in the current OS thread. Supported code: source text. Copyright ========= This document has been placed in the public domain. [View Less]

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