Mailman 3 August 2015 - Python-checkins

peps: Allocate PEP 502 for Mike Miller's proposal
by chris.angelico Aug. 31, 2015

Aug. 31, 2015

https://hg.python.org/peps/rev/e980e47d452f changeset: 6025:e980e47d452f user: Chris Angelico <rosuav(a)gmail.com> date: Tue Sep 01 03:26:19 2015 +1000 summary: Allocate PEP 502 for Mike Miller's proposal files: pep-0502.txt | 846 +++++++++++++++++++++++++++++++++++++++ 1 files changed, 846 insertions(+), 0 deletions(-) diff --git a/pep-0502.txt b/pep-0502.txt new file mode 100644 --- /dev/null +++ b/pep-0502.txt @@ -0,0 +1,846 @@ +PEP: 502 +Title: String Interpolation Redux +Version: $Revision$ +Last-Modified: $Date$ +Author: Mike G. Miller +Status: Draft +Type: Standards Track +Content-Type: text/x-rst +Created: 10-Aug-2015 +Python-Version: 3.6 + +Note: Open issues below are stated with a question mark (?), +and are therefore searchable. + + +Abstract +======== + +This proposal describes a new string interpolation feature for Python, +called an *expression-string*, +that is both concise and powerful, +improves readability in most cases, +yet does not conflict with existing code. + +To achieve this end, +a new string prefix is introduced, +which expands at compile-time into an equivalent expression-string object, +with requested variables from its context passed as keyword arguments. +At runtime, +the new object uses these passed values to render a string to given +specifications, building on `the existing syntax`_ of ``str.format()``:: + + >>> location = 'World' + >>> e'Hello, {location} !' # new prefix: e'' + 'Hello, World !' # interpolated result + +.. _the existing syntax: https://docs.python.org/3/library/string.html#format-string-syntax + +This PEP does not recommend to remove or deprecate any of the existing string +formatting mechanisms. + + +Motivation +========== + +Though string formatting and manipulation features are plentiful in Python, +one area where it falls short +is the lack of a convenient string interpolation syntax. +In comparison to other dynamic scripting languages +with similar use cases, +the amount of code necessary to build similar strings is substantially higher, +while at times offering lower readability due to verbosity, dense syntax, +or identifier duplication. [1]_ + +Furthermore, replacement of the print statement with the more consistent print +function of Python 3 (PEP 3105) has added one additional minor burden, +an additional set of parentheses to type and read. +Combined with the verbosity of current formatting solutions, +this puts an otherwise simple language at an unfortunate disadvantage to its +peers:: + + echo "Hello, user: $user, id: $id, on host: $hostname" # bash + say "Hello, user: $user, id: $id, on host: $hostname"; # perl + puts "Hello, user: #{user}, id: #{id}, on host: #{hostname}\n" # ruby + # 80 ch -->| + # Python 3, str.format with named parameters + print('Hello, user: {user}, id: {id}, on host: {hostname}'.format(**locals())) + + # Python 3, variation B, worst case + print('Hello, user: {user}, id: {id}, on host: {hostname}'.format(user=user, + id=id, + hostname= + hostname)) + +In Python, the formatting and printing of a string with multiple variables in a +single line of code of standard width is noticeably harder and more verbose, +indentation often exacerbating the issue. + +For use cases such as smaller projects, systems programming, +shell script replacements, and even one-liners, +where message formatting complexity has yet to be encapsulated, +this verbosity has likely lead a significant number of developers and +administrators to choose other languages over the years. + + +Rationale +========= + + +Naming +------ + +The term expression-string was chosen because other applicable terms, +such as format-string and template are already well used in the Python standard +library. + +The string prefix itself, ``e''`` was chosen to demonstrate that the +specification enables expressions, +is not limited to ``str.format()`` syntax, +and also does not lend itself to `the shorthand term`_ "f-string". +It is also slightly easier to type than other choices such as ``_''`` and +``i''``, +while perhaps `less odd-looking`_ to C-developers. +``printf('')`` vs. ``print(f'')``. + +.. _the shorthand term: reference_needed +.. _less odd-looking: https://mail.python.org/pipermail/python-dev/2015-August/141147.html + + + +Goals +------------- + +The design goals of expression-strings are as follows: + +#. Eliminate need to pass variables manually. +#. Eliminate repetition of identifiers and redundant parentheses. +#. Reduce awkward syntax, punctuation characters, and visual noise. +#. Improve readability and eliminate mismatch errors, + by prefering named parameters to positional arguments. +#. Avoid need for ``locals()`` and ``globals()`` usage, + instead parsing the given string for named parameters, + then passing them automatically. [2]_ [3]_ + + +Limitations +------------- + +In contrast to other languages that take design cues from Unix and its +shells, +and in common with Javascript, +Python specified both single (``'``) and double (``"``) ASCII quote +characters to enclose strings. +It is not reasonable to choose one of them now to enable interpolation, +while leaving the other for uninterpolated strings. +"Backtick" characters (`````) are also `constrained by history`_ as a shortcut +for ``repr()``. + +This leaves a few remaining options for the design of such a feature: + +* An operator, as in printf-style string formatting via ``%``. +* A class, such as ``string.Template()``. +* A function, such as ``str.format()``. +* New syntax +* A new string prefix marker, such as the well-known ``r''`` or ``u''``. + +The first three options above currently work well. +Each has specific use cases and drawbacks, +yet also suffer from the verbosity and visual noise mentioned previously. +All are discussed in the next section. + +.. _constrained by history: https://mail.python.org/pipermail/python-ideas/2007-January/000054.html + +Background +------------- + +This proposal builds on several existing techniques and proposals and what +we've collectively learned from them. + +The following examples focus on the design goals of readability and +error-prevention using named parameters. +Let's assume we have the following dictionary, +and would like to print out its items as an informative string for end users:: + + >>> params = {'user': 'nobody', 'id': 9, 'hostname': 'darkstar'} + + +Printf-style formatting +''''''''''''''''''''''' + +This `venerable technique`_ continues to have its uses, +such as with byte-based protocols, +simplicity in simple cases, +and familiarity to many programmers:: + + >>> 'Hello, user: %(user)s, id: %(id)s, on host: %(hostname)s' % params + 'Hello, user: nobody, id: 9, on host: darkstar' + +In this form, considering the prerequisite dictionary creation, +the technique is verbose, a tad noisy, +and relatively readable. +Additional issues are that an operator can only take one argument besides the +original string, +meaning multiple parameters must be passed in a tuple or dictionary. +Also, it is relatively easy to make an error in the number of arguments passed, +the expected type, +have a missing key, +or forget the trailing type, e.g. (``s`` or ``d``). + +.. _venerable technique: https://docs.python.org/3/library/stdtypes.html#printf-style-string-formatt… + + +string.Template +''''''''''''''' + +The ``string.Template`` `class from`_ PEP 292 +(Simpler String Substitutions) +is a purposely simplified design, +using familiar shell interpolation syntax, +with `safe-substitution feature`_, +that finds its main use cases in shell and internationalization tools:: + + Template('Hello, user: $user, id: ${id}, on host: $hostname').substitute(params) + +Also verbose, however the string itself is readable. +Though functionality is limited, +it meets its requirements well. +It isn't powerful enough for many cases, +and that helps keep inexperienced users out of trouble, +as well as avoiding issues with moderately-trusted input (i18n) from +third-parties. +It unfortunately takes enough code to discourage its use for ad-hoc string +interpolation, +unless encapsulated in a `convenience library`_ such as ``flufl.i18n``. + +.. _class from: https://docs.python.org/3/library/string.html#template-strings +.. _safe-substitution feature: https://docs.python.org/3/library/string.html#string.Template.safe_substitu… +.. _convenience library: http://pythonhosted.org/flufl.i18n/ + + +PEP 215 - String Interpolation +'''''''''''''''''''''''''''''' + +PEP 215 was a former proposal of which this one shares a lot in common. +Apparently, the world was not ready for it at the time, +but considering recent support in a number of other languages, +its day may have come. + +The large number of dollar sign (``$``) characters it included may have +led it to resemble Python's arch-nemesis Perl, +and likely contributed to the PEP's lack of acceptance. +It was superseded by the following proposal. + + +str.format() +'''''''''''' + +The ``str.format()`` `syntax of`_ PEP 3101 is the most recent and modern of the +existing options. +It is also more powerful and usually easier to read than the others. +It avoids many of the drawbacks and limits of the previous techniques. + +However, due to its necessary function call and parameter passing, +it runs from verbose to very verbose in various situations with +string literals:: + + >>> 'Hello, user: {user}, id: {id}, on host: {hostname}'.format(**params) + 'Hello, user: nobody, id: 9, on host: darkstar' + + # when using keyword args, var name shortening sometimes needed to fit :/ + >>> 'Hello, user: {user}, id: {id}, on host: {host}'.format(user=user, + id=id, + host=hostname) + 'Hello, user: nobody, id: 9, on host: darkstar' + +.. _syntax of: https://docs.python.org/3/library/string.html#format-string-syntax + + +PEP 498 -- Literal String Formatting +'''''''''''''''''''''''''''''''''''' + +PEP 498 discusses and delves partially into implementation details of +expression-strings, +which it calls f-strings, +the idea and syntax +(with exception of the prefix letter) +of which is identical to that discussed here. +The resulting compile-time transformation however +returns a string joined from parts at runtime, +rather than an object. + +It also, somewhat controversially to those first exposed to it, +introduces the idea that these strings shall be augmented with support for +arbitrary expressions, +which is discussed further in the following sections. + + +PEP 501 -- Translation ready string interpolation +''''''''''''''''''''''''''''''''''''''''''''''''' + +The complimentary PEP 501 brings internationalization into the discussion as a +first-class concern, with its proposal of i-strings, +``string.Template`` syntax integration compatible with ES6 (Javascript), +deferred rendering, +and a similar object return value. + + +Implementations in Other Languages +---------------------------------- + +String interpolation is now well supported by various programming languages +used in multiple industries, +and is converging into a standard of sorts. +It is centered around ``str.format()`` style syntax in minor variations, +with the addition of arbitrary expressions to expand utility. + +In the `Motivation`_ section it was shown how convenient interpolation syntax +existed in Bash, Perl, and Ruby. +Let's take a look at their expression support. + + +Bash +'''' + +Bash supports a number of arbitrary, even recursive constructs inside strings:: + + > echo "user: $USER, id: $((id + 6)) on host: $(echo is $(hostname))" + user: nobody, id: 15 on host: is darkstar + +* Explicit interpolation within double quotes. +* Direct environment variable access supported. +* Arbitrary expressions are supported. [4]_ +* External process execution and output capture supported. [5]_ +* Recursive expressions are supported. + + +Perl +'''' + + +Perl also has arbitrary expression constructs, perhaps not as well known:: + + say "I have @{[$id + 6]} guanacos."; # lists + say "I have ${\($id + 6)} guanacos."; # scalars + say "Hello { @names.join(', ') } how are you?"; # Perl 6 version + +* Explicit interpolation within double quotes. +* Arbitrary expressions are supported. [6]_ [7]_ + + +Ruby +'''' + +Ruby allows arbitrary expressions in its interpolated strings:: + + puts "One plus one is two: #{1 + 1}\n" + +* Explicit interpolation within double quotes. +* Arbitrary expressions are supported. [8]_ [9]_ +* Possible to change delimiter chars with ``%``. +* See the Reference Implementation(s) section for an implementation in Python. + + +Others +'''''' + +Let's look at some less-similar modern languages recently implementing string +interpolation. + + +Scala +''''' + +`Scala interpolation`_ is directed through string prefixes. +Each prefix has a different result:: + + s"Hello, $name ${1 + 1}" # arbitrary + f"$name%s is $height%2.2f meters tall" # printf-style + raw"a\nb" # raw, like r'' + +These prefixes may also be implemented by the user, +by extending Scala's ``StringContext`` class. + +* Explicit interpolation within double quotes with literal prefix. +* User implemented prefixes supported. +* Arbitrary expressions are supported. + +.. _Scala interpolation: http://docs.scala-lang.org/overviews/core/string-interpolation.html + + +ES6 (Javascript) +''''''''''''''''''' + +Designers of `Template strings`_ faced the same issue as Python where single +and double quotes were taken. +Unlike Python however, "backticks" were not. +They were chosen as part of the ECMAScript 2015 (ES6) standard:: + + console.log(`Fifteen is ${a + b} and\nnot ${2 * a + b}.`); + +Custom prefixes are also supported by implementing a function the same name +as the tag:: + + function tag(strings, ...values) { + console.log(strings.raw[0]); // raw string is also available + return "Bazinga!"; + } + tag`Hello ${ a + b } world ${ a * b}`; + +* Explicit interpolation within backticks. +* User implemented prefixes supported. +* Arbitrary expressions are supported. + +.. _Template strings: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/template_… + +C#, Version 6 +''''''''''''' + +C# has a useful new `interpolation feature`_ as well, +with some ability to `customize interpolation`_ via the ``IFormattable`` +interface:: + + $"{person.Name, 20} is {person.Age:D3} year{(p.Age == 1 ? "" : "s")} old."; + +* Explicit interpolation with double quotes and ``$`` prefix. +* Custom interpolations are available. +* Arbitrary expressions are supported. + +.. _interpolation feature: https://msdn.microsoft.com/en-us/library/Dn961160.aspx +.. _customize interpolation: http://www.thomaslevesque.com/2015/02/24/customizing-string-interpolation-i… + +Apple's Swift +''''''''''''' + +Arbitrary `interpolation under Swift`_ is available on all strings:: + + let multiplier = 3 + let message = "\(multiplier) times 2.5 is \(Double(multiplier) * 2.5)" + // message is "3 times 2.5 is 7.5" + +* Implicit interpolation with double quotes. +* Arbitrary expressions are supported. +* Cannot contain CR/LF. + +.. _interpolation under Swift: https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swif… + + +Additional examples +''''''''''''''''''' + +A number of additional examples may be `found at Wikipedia`_. + +.. _found at Wikipedia: https://en.wikipedia.org/wiki/String_interpolation#Examples + +Now that background and imlementation history have been covered, +let's continue on for a solution. + + +New Syntax +---------- + +This should be an option of last resort, +as every new syntax feature has a cost in terms of real-estate in a brain it +inhabits. +There is one alternative left on our list of possibilities, +which follows. + + +New String Prefix +----------------- + +Given the history of string formatting in Python, +backwards-compatibility, +implementations in other languages, +and the avoidance of new syntax unless necessary, +an acceptable design is reached through elimination +rather than unique insight. +Therefore, we choose to explicitly mark interpolated string literals with a +string prefix. + +We also choose an expression syntax that reuses and builds on the strongest of +the existing choices, +``str.format()`` to avoid further duplication. + + +Specification +============= + +String literals with the prefix of ``e`` shall be converted at compile-time to +the construction of an ``estr`` (perhaps ``types.ExpressionString``?) object. +Strings and values are parsed from the literal and passed as tuples to the +constructor:: + + >>> location = 'World' + >>> e'Hello, {location} !' + + # becomes + # estr('Hello, {location} !', # template + ('Hello, ', ' !'), # string fragments + ('location',), # expressions + ('World',), # values + ) + +The object interpolates its result immediately at run-time:: + + 'Hello, World !' + + +ExpressionString Objects +------------------------ + +The ExpressionString object supports both immediate and deferred rendering of +its given template and parameters. +It does this by immediately rendering its inputs to its internal string and +``.rendered`` string member (still necessary?), +useful in the majority of use cases. +To allow for deferred rendering and caller-specified escaping, +all inputs are saved for later inspection, +with convenience methods available. + +Notes: + +* Inputs are saved to the object as ``.template`` and ``.context`` members + for later use. +* No explicit ``str(estr)`` call is necessary to render the result, + though doing so might be desired to free resources if significant. +* Additional or deferred rendering is available through the ``.render()`` + method, which allows template and context to be overriden for flexibility. +* Manual escaping of potentially dangerous input is available through the + ``.escape(escape_function)`` method, + the rules of which may therefore be specified by the caller. + The given function should both accept and return a single modified string. + +* A sample Python implementation can `found at Bitbucket`_: + +.. _found at Bitbucket: https://bitbucket.org/mixmastamyk/docs/src/default/pep/estring_demo.py + + +Inherits From ``str`` Type +''''''''''''''''''''''''''' + +Inheriting from the ``str`` class is one of the techniques available to improve +compatibility with code expecting a string object, +as it will pass an ``isinstance(obj, str)`` test. +ExpressionString implements this and also renders its result into the "raw" +string of its string superclass, +providing compatibility with a majority of code. + + +Interpolation Syntax +-------------------- + +The strongest of the existing string formatting syntaxes is chosen, +``str.format()`` as a base to build on. [10]_ [11]_ + +.. + +* Additionally, single arbitrary expressions shall also be supported inside + braces as an extension:: + + >>> e'My age is {age + 1} years.' + + See below for section on safety. + +* Triple quoted strings with multiple lines shall be supported:: + + >>> e'''Hello, + {location} !''' + 'Hello,\n World !' + +* Adjacent implicit concatenation shall be supported; + interpolation does not `not bleed into`_ other strings:: + + >>> 'Hello {1, 2, 3} ' e'{location} !' + 'Hello {1, 2, 3} World !' + +* Additional implementation details, + for example expression and error-handling, + are specified in the compatible PEP 498. + +.. _not bleed into: https://mail.python.org/pipermail/python-ideas/2015-July/034763.html + + +Composition with Other Prefixes +------------------------------- + +* Expression-strings apply to unicode objects only, + therefore ``u''`` is never needed. + Should it be prevented? + +* Bytes objects are not included here and do not compose with e'' as they + do not support ``__format__()``. + +* Complimentary to raw strings, + backslash codes shall not be converted in the expression-string, + when combined with ``r''`` as ``re''``. + + +Examples +-------- + +A more complicated example follows:: + + n = 5; # t0, t1 = … TODO + a = e"Sliced {n} onions in {t1-t0:.3f} seconds." + # returns the equvalent of + estr("Sliced {n} onions in {t1-t0:.3f} seconds", # template + ('Sliced ', ' onions in ', ' seconds'), # strings + ('n', 't1-t0:.3f'), # expressions + (5, 0.555555) # values + ) + +With expressions only:: + + b = e"Three random numbers: {rand()}, {rand()}, {rand()}." + # returns the equvalent of + estr("Three random numbers: {rand():f}, {rand():f}, {rand():}.", # template + ('Three random numbers: ', ', ', ', ', '.'), # strings + ('rand():f', 'rand():f', 'rand():f'), # expressions + (rand(), rand(), rand()) # values + ) + + +Safety +----------- + +In this section we will describe the safety situation and precautions taken +in support of expression-strings. + +#. Only string literals shall be considered here, + not variables to be taken as input or passed around, + making external attacks difficult to accomplish. + + * ``str.format()`` `already handles`_ this use-case. + * Direct instantiation of the ExpressionString object with non-literal input + shall not be allowed. (Practicality?) + +#. Neither ``locals()`` nor ``globals()`` are necessary nor used during the + transformation, + avoiding leakage of information. + +#. To eliminate complexity as well as ``RuntimeError`` (s) due to recursion + depth, recursive interpolation is not supported. + +#. Restricted characters or expression classes?, such as ``=`` for assignment. + +However, +mistakes or malicious code could be missed inside string literals. +Though that can be said of code in general, +that these expressions are inside strings means they are a bit more likely +to be obscured. + +.. _already handles: https://mail.python.org/pipermail/python-ideas/2015-July/034729.html + + +Mitigation via tools +'''''''''''''''''''' + +The idea is that tools or linters such as pyflakes, pylint, or Pycharm, +could check inside strings for constructs that exceed project policy. +As this is a common task with languages these days, +tools won't have to implement this feature solely for Python, +significantly shortening time to implementation. + +Additionally the Python interpreter could check(?) and warn with appropriate +command-line parameters passed. + + +Backwards Compatibility +----------------------- + +By using existing syntax and avoiding use of current or historical features, +expression-strings (and any associated sub-features), +were designed so as to not interfere with existing code and is not expected +to cause any issues. + + +Postponed Ideas +--------------- + +Internationalization +'''''''''''''''''''' + +Though it was highly desired to integrate internationalization support, +(see PEP 501), +the finer details diverge at almost every point, +making a common solution unlikely: [15]_ + +* Use-cases +* Compile and run-time tasks +* Interpolation Syntax +* Intended audience +* Security policy + +Rather than try to fit a "square peg in a round hole," +this PEP attempts to allow internationalization to be supported in the future +by not preventing it. +In this proposal, +expression-string inputs are saved for inspection and re-rendering at a later +time, +allowing for their use by an external library of any sort. + + +Rejected Ideas +-------------- + +Restricting Syntax to ``str.format()`` Only +''''''''''''''''''''''''''''''''''''''''''' + +This was deemed not enough of a solution to the problem. +It can be seen in the `Implementations in Other Languages`_ section that the +developer community at large tends to agree. + +The common `arguments against`_ arbitrary expresssions were: + +#. YAGNI, "You ain't gonna need it." +#. The change is not congruent with historical Python conservatism. +#. Postpone - can implement in a future version if need is demonstrated. + +.. _arguments against: https://mail.python.org/pipermail/python-ideas/2015-August/034913.html + + +Additional/Custom String-Prefixes +''''''''''''''''''''''''''''''''' + +As seen in the `Implementations in Other Languages`_ section, +many modern languages have extensible string prefixes with a common interface. +This could be a way to generalize and reduce lines of code in common +situations. +Examples are found in ES6 (Javascript), Scala, Nim, and C# +(to a lesser extent). +This was rejected by the BDFL. [14]_ + + +Automated Escaping of Input Variables +''''''''''''''''''''''''''''''''''''' + +While helpful in some cases, +this was thought to create too much uncertainty of when and where string +expressions could be used safely or not. +The concept was also difficult to describe to others. [12]_ + +Always consider expression-string variables to be unescaped, +unless the developer has explicitly escaped them. + + +Environment Access and Command Substitution +''''''''''''''''''''''''''''''''''''''''''' + +For systems programming and shell-script replacements, +it would be useful to handle environment variables and capture output of +commands directly in an expression string. +This was rejected as not important enough, +and looking too much like bash/perl, +which could encourage bad habits. [13]_ + + +Reference Implementation(s) +=========================== + +An expression-string implementation is currently attached to PEP 498, +under the ``f''`` prefix, +and may be available in nightly builds. + +A Python implementation of Ruby interpolation `is also available`_, +which is similar to this proposal. +It uses the codecs module to do its work:: + + ＞ pip install interpy + + # coding: interpy + location = 'World' + print("Hello #{location}.") + +.. _is also available: https://github.com/syrusakbary/interpy + + +Acknowledgements +================ + +* Eric V. Smith for providing invaluable implementation work and design + opinions, helping to focus this PEP. +* Others on the python-ideas mailing list for rejecting the craziest of ideas, + also helping to achieve focus. + + +References +========== + +.. [1] Briefer String Format + + (https://mail.python.org/pipermail/python-ideas/2015-July/034659.html) + + +.. [2] Briefer String Format + + (https://mail.python.org/pipermail/python-ideas/2015-July/034669.html) + +.. [3] Briefer String Format + + (https://mail.python.org/pipermail/python-ideas/2015-July/034701.html) + +.. [4] Bash Docs + + (http://www.tldp.org/LDP/abs/html/arithexp.html) + +.. [5] Bash Docs + + (http://www.tldp.org/LDP/abs/html/commandsub.html) + +.. [6] Perl Cookbook + + (http://docstore.mik.ua/orelly/perl/cookbook/ch01_11.htm) + +.. [7] Perl Docs + + (http://perl6maven.com/perl6-scalar-array-and-hash-interpolation) + +.. [8] Ruby Docs + + (http://ruby-doc.org/core-2.1.1/doc/syntax/literals_rdoc.html#label-Strings) + +.. [9] Ruby Docs + + (https://en.wikibooks.org/wiki/Ruby_Programming/Syntax/Literals#Interpolation) + +.. [10] Python Str.Format Syntax + + (https://docs.python.org/3/library/string.html#format-string-syntax) + +.. [11] Python Format-Spec Mini Language + + (https://docs.python.org/3/library/string.html#format-specification-mini-lan…) + +.. [12] Escaping of Input Variables + + (https://mail.python.org/pipermail/python-ideas/2015-August/035532.html) + +.. [13] Environment Access and Command Substitution + + (https://mail.python.org/pipermail/python-ideas/2015-August/035554.html) + +.. [14] Extensible String Prefixes + + (https://mail.python.org/pipermail/python-ideas/2015-August/035336.html) + + +.. [15] Literal String Formatting + + (https://mail.python.org/pipermail/python-dev/2015-August/141289.html) + + +Copyright +========= + +This document has been placed in the public domain. + + +.. + Local Variables: + mode: indented-text + indent-tabs-mode: nil + sentence-end-double-space: t + fill-column: 70 + coding: utf-8 + End: -- Repository URL: https://hg.python.org/peps

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cpython (3.5): Make asyncio provisional
by yury.selivanov Aug. 31, 2015

Aug. 31, 2015

https://hg.python.org/cpython/rev/833db9e2ed14 changeset: 97561:833db9e2ed14 branch: 3.5 parent: 97558:606082fa2804 user: Yury Selivanov <yselivanov(a)sprymix.com> date: Mon Aug 31 11:42:31 2015 -0400 summary: Make asyncio provisional files: Doc/library/asyncio.rst | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/Doc/library/asyncio.rst b/Doc/library/asyncio.rst --- a/Doc/library/asyncio.rst +++ b/Doc/library/asyncio.rst @@ -4,6 +4,13 @@ .. module:: asyncio :synopsis: Asynchronous I/O, event loop, coroutines and tasks. +.. note:: + + The asyncio package has been included in the standard library on a + :term:`provisional basis <provisional package>`. Backwards incompatible + changes (up to and including removal of the module) may occur if deemed + necessary by the core developers. + .. versionadded:: 3.4 **Source code:** :source:`Lib/asyncio/` -- Repository URL: https://hg.python.org/cpython

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cpython (merge 3.5 -> default): Merge 3.5
by yury.selivanov Aug. 31, 2015

Aug. 31, 2015

https://hg.python.org/cpython/rev/afdfb9d53bec changeset: 97562:afdfb9d53bec parent: 97559:501c9ab07996 parent: 97561:833db9e2ed14 user: Yury Selivanov <yselivanov(a)sprymix.com> date: Mon Aug 31 11:45:11 2015 -0400 summary: Merge 3.5 files: Doc/library/asyncio.rst | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/Doc/library/asyncio.rst b/Doc/library/asyncio.rst --- a/Doc/library/asyncio.rst +++ b/Doc/library/asyncio.rst @@ -4,6 +4,13 @@ .. module:: asyncio :synopsis: Asynchronous I/O, event loop, coroutines and tasks. +.. note:: + + The asyncio package has been included in the standard library on a + :term:`provisional basis <provisional package>`. Backwards incompatible + changes (up to and including removal of the module) may occur if deemed + necessary by the core developers. + .. versionadded:: 3.4 **Source code:** :source:`Lib/asyncio/` -- Repository URL: https://hg.python.org/cpython

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Benchmark Results for Python Default 2015-08-31
by lp_benchmark_robot Aug. 31, 2015

Aug. 31, 2015

Results for project python_default-nightly, build date 2015-08-31 06:01:58 commit: 6463279d1358c3d49248ef14e36ef29d120dd51b revision date: 2015-08-31 00:42:59 environment: Haswell-EP cpu: Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz 2x18 cores, stepping 2, LLC 45 MB mem: 128 GB os: CentOS 7.1 kernel: Linux 3.10.0-229.4.2.el7.x86_64 Baseline results were generated using release v3.4.3, with hash b4cbecbc0781e89a309d03b60a1f75f8499250e6 from 2015-02-25 12:15:33+00:00 ------------------------------------------------------------------------------------------ benchmark RSD* change since change since current rev with last run v3.4.3 regrtest PGO ------------------------------------------------------------------------------------------ :-) django_v2 0.40608% 0.21446% 8.14571% 19.04110% :-( pybench 0.19452% -0.02602% -2.45927% 9.15137% :-( regex_v8 2.86216% -0.14215% -3.17365% 4.53947% :-| nbody 0.13554% -0.46917% -1.33943% 10.33270% :-| json_dump_v2 0.31690% 1.73772% -1.04898% 12.85790% :-| normal_startup 1.11541% 0.28281% -0.40770% 5.37791% ------------------------------------------------------------------------------------------ Note: Benchmark results are measured in seconds. * Relative Standard Deviation (Standard Deviation/Average) Our lab does a nightly source pull and build of the Python project and measures performance changes against the previous stable version and the previous nightly measurement. This is provided as a service to the community so that quality issues with current hardware can be identified quickly. Intel technologies' features and benefits depend on system configuration and may require enabled hardware, software or service activation. Performance varies depending on system configuration. No license (express or implied, by estoppel or otherwise) to any intellectual property rights is granted by this document. Intel disclaims all express and implied warranties, including without limitation, the implied warranties of merchantability, fitness for a particular purpose, and non-infringement, as well as any warranty arising from course of performance, course of dealing, or usage in trade. This document may contain information on products, services and/or processes in development. Contact your Intel representative to obtain the latest forecast, schedule, specifications and roadmaps. The products and services described may contain defects or errors known as errata which may cause deviations from published specifications. Current characterized errata are available on request. (C) 2015 Intel Corporation.

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cpython (merge 3.5 -> default): Issue #24952: Merge 3.5 into 3.6
by martin.panter Aug. 31, 2015

Aug. 31, 2015

https://hg.python.org/cpython/rev/501c9ab07996 changeset: 97559:501c9ab07996 parent: 97555:6463279d1358 parent: 97558:606082fa2804 user: Martin Panter <vadmium> date: Mon Aug 31 03:26:46 2015 +0000 summary: Issue #24952: Merge 3.5 into 3.6 files: Doc/library/_thread.rst | 3 ++- Doc/library/threading.rst | 3 ++- Misc/ACKS | 1 + Misc/NEWS | 3 +++ 4 files changed, 8 insertions(+), 2 deletions(-) diff --git a/Doc/library/_thread.rst b/Doc/library/_thread.rst --- a/Doc/library/_thread.rst +++ b/Doc/library/_thread.rst @@ -93,7 +93,8 @@ Return the thread stack size used when creating new threads. The optional *size* argument specifies the stack size to be used for subsequently created threads, and must be 0 (use platform or configured default) or a positive - integer value of at least 32,768 (32 KiB). If changing the thread stack size is + integer value of at least 32,768 (32 KiB). If *size* is not specified, + 0 is used. If changing the thread stack size is unsupported, a :exc:`RuntimeError` is raised. If the specified stack size is invalid, a :exc:`ValueError` is raised and the stack size is unmodified. 32 KiB is currently the minimum supported stack size value to guarantee sufficient diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst --- a/Doc/library/threading.rst +++ b/Doc/library/threading.rst @@ -89,7 +89,8 @@ Return the thread stack size used when creating new threads. The optional *size* argument specifies the stack size to be used for subsequently created threads, and must be 0 (use platform or configured default) or a positive - integer value of at least 32,768 (32 KiB). If changing the thread stack size is + integer value of at least 32,768 (32 KiB). If *size* is not specified, + 0 is used. If changing the thread stack size is unsupported, a :exc:`RuntimeError` is raised. If the specified stack size is invalid, a :exc:`ValueError` is raised and the stack size is unmodified. 32 KiB is currently the minimum supported stack size value to guarantee sufficient diff --git a/Misc/ACKS b/Misc/ACKS --- a/Misc/ACKS +++ b/Misc/ACKS @@ -914,6 +914,7 @@ Simon Mathieu Laura Matson Graham Matthews +mattip Martin Matusiak Dieter Maurer Daniel May diff --git a/Misc/NEWS b/Misc/NEWS --- a/Misc/NEWS +++ b/Misc/NEWS @@ -64,6 +64,9 @@ Documentation ------------- +- Issue #24952: Clarify the default size argument of stack_size() in + the "threading" and "_thread" modules. Patch from Mattip. + Tests ----- -- Repository URL: https://hg.python.org/cpython

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cpython (merge 3.4 -> 3.5): Issue #24952: Merge 3.4 into 3.5
by martin.panter Aug. 31, 2015

Aug. 31, 2015

https://hg.python.org/cpython/rev/606082fa2804 changeset: 97558:606082fa2804 branch: 3.5 parent: 97554:b5434aff4e84 parent: 97557:328383905eaf user: Martin Panter <vadmium> date: Mon Aug 31 03:25:34 2015 +0000 summary: Issue #24952: Merge 3.4 into 3.5 files: Doc/library/_thread.rst | 3 ++- Doc/library/threading.rst | 3 ++- Misc/ACKS | 1 + Misc/NEWS | 3 +++ 4 files changed, 8 insertions(+), 2 deletions(-) diff --git a/Doc/library/_thread.rst b/Doc/library/_thread.rst --- a/Doc/library/_thread.rst +++ b/Doc/library/_thread.rst @@ -93,7 +93,8 @@ Return the thread stack size used when creating new threads. The optional *size* argument specifies the stack size to be used for subsequently created threads, and must be 0 (use platform or configured default) or a positive - integer value of at least 32,768 (32 KiB). If changing the thread stack size is + integer value of at least 32,768 (32 KiB). If *size* is not specified, + 0 is used. If changing the thread stack size is unsupported, a :exc:`RuntimeError` is raised. If the specified stack size is invalid, a :exc:`ValueError` is raised and the stack size is unmodified. 32 KiB is currently the minimum supported stack size value to guarantee sufficient diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst --- a/Doc/library/threading.rst +++ b/Doc/library/threading.rst @@ -89,7 +89,8 @@ Return the thread stack size used when creating new threads. The optional *size* argument specifies the stack size to be used for subsequently created threads, and must be 0 (use platform or configured default) or a positive - integer value of at least 32,768 (32 KiB). If changing the thread stack size is + integer value of at least 32,768 (32 KiB). If *size* is not specified, + 0 is used. If changing the thread stack size is unsupported, a :exc:`RuntimeError` is raised. If the specified stack size is invalid, a :exc:`ValueError` is raised and the stack size is unmodified. 32 KiB is currently the minimum supported stack size value to guarantee sufficient diff --git a/Misc/ACKS b/Misc/ACKS --- a/Misc/ACKS +++ b/Misc/ACKS @@ -914,6 +914,7 @@ Simon Mathieu Laura Matson Graham Matthews +mattip Martin Matusiak Dieter Maurer Daniel May diff --git a/Misc/NEWS b/Misc/NEWS --- a/Misc/NEWS +++ b/Misc/NEWS @@ -41,6 +41,9 @@ Documentation ------------- +- Issue #24952: Clarify the default size argument of stack_size() in + the "threading" and "_thread" modules. Patch from Mattip. + - Issue #23725: Overhaul tempfile docs. Note deprecated status of mktemp. Patch from Zbigniew Jędrzejewski-Szmek. -- Repository URL: https://hg.python.org/cpython

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cpython (3.4): Issue #24952: Clarify default argument of stack_size() in threading, _thread
by martin.panter Aug. 31, 2015

Aug. 31, 2015

https://hg.python.org/cpython/rev/328383905eaf changeset: 97557:328383905eaf branch: 3.4 parent: 97553:a892c67fa0eb user: Martin Panter <vadmium> date: Mon Aug 31 03:15:52 2015 +0000 summary: Issue #24952: Clarify default argument of stack_size() in threading, _thread Patch from Mattip. files: Doc/library/_thread.rst | 3 ++- Doc/library/threading.rst | 3 ++- Misc/ACKS | 1 + Misc/NEWS | 3 +++ 4 files changed, 8 insertions(+), 2 deletions(-) diff --git a/Doc/library/_thread.rst b/Doc/library/_thread.rst --- a/Doc/library/_thread.rst +++ b/Doc/library/_thread.rst @@ -93,7 +93,8 @@ Return the thread stack size used when creating new threads. The optional *size* argument specifies the stack size to be used for subsequently created threads, and must be 0 (use platform or configured default) or a positive - integer value of at least 32,768 (32 KiB). If changing the thread stack size is + integer value of at least 32,768 (32 KiB). If *size* is not specified, + 0 is used. If changing the thread stack size is unsupported, a :exc:`RuntimeError` is raised. If the specified stack size is invalid, a :exc:`ValueError` is raised and the stack size is unmodified. 32 KiB is currently the minimum supported stack size value to guarantee sufficient diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst --- a/Doc/library/threading.rst +++ b/Doc/library/threading.rst @@ -89,7 +89,8 @@ Return the thread stack size used when creating new threads. The optional *size* argument specifies the stack size to be used for subsequently created threads, and must be 0 (use platform or configured default) or a positive - integer value of at least 32,768 (32 KiB). If changing the thread stack size is + integer value of at least 32,768 (32 KiB). If *size* is not specified, + 0 is used. If changing the thread stack size is unsupported, a :exc:`RuntimeError` is raised. If the specified stack size is invalid, a :exc:`ValueError` is raised and the stack size is unmodified. 32 KiB is currently the minimum supported stack size value to guarantee sufficient diff --git a/Misc/ACKS b/Misc/ACKS --- a/Misc/ACKS +++ b/Misc/ACKS @@ -888,6 +888,7 @@ Simon Mathieu Laura Matson Graham Matthews +mattip Martin Matusiak Dieter Maurer Daniel May diff --git a/Misc/NEWS b/Misc/NEWS --- a/Misc/NEWS +++ b/Misc/NEWS @@ -456,6 +456,9 @@ Documentation ------------- +- Issue #24952: Clarify the default size argument of stack_size() in + the "threading" and "_thread" modules. Patch from Mattip. + - Issue #24808: Update the types of some PyTypeObject fields. Patch by Joseph Weston. -- Repository URL: https://hg.python.org/cpython

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cpython (2.7): Issue #24952: Clarify default argument of stack_size() in threading, thread
by martin.panter Aug. 31, 2015

Aug. 31, 2015

https://hg.python.org/cpython/rev/79afd50396c5 changeset: 97560:79afd50396c5 branch: 2.7 parent: 97556:62a3c600f3cf user: Martin Panter <vadmium> date: Mon Aug 31 03:40:59 2015 +0000 summary: Issue #24952: Clarify default argument of stack_size() in threading, thread Patch from Mattip. files: Doc/library/thread.rst | 3 ++- Doc/library/threading.rst | 3 ++- Misc/ACKS | 1 + Misc/NEWS | 3 +++ 4 files changed, 8 insertions(+), 2 deletions(-) diff --git a/Doc/library/thread.rst b/Doc/library/thread.rst --- a/Doc/library/thread.rst +++ b/Doc/library/thread.rst @@ -98,7 +98,8 @@ Return the thread stack size used when creating new threads. The optional *size* argument specifies the stack size to be used for subsequently created threads, and must be 0 (use platform or configured default) or a positive - integer value of at least 32,768 (32kB). If changing the thread stack size is + integer value of at least 32,768 (32kB). If *size* is not specified, + 0 is used. If changing the thread stack size is unsupported, the :exc:`error` exception is raised. If the specified stack size is invalid, a :exc:`ValueError` is raised and the stack size is unmodified. 32kB is currently the minimum supported stack size value to guarantee sufficient diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst --- a/Doc/library/threading.rst +++ b/Doc/library/threading.rst @@ -194,7 +194,8 @@ Return the thread stack size used when creating new threads. The optional *size* argument specifies the stack size to be used for subsequently created threads, and must be 0 (use platform or configured default) or a positive - integer value of at least 32,768 (32kB). If changing the thread stack size is + integer value of at least 32,768 (32 KiB). If *size* is not specified, + 0 is used. If changing the thread stack size is unsupported, a :exc:`ThreadError` is raised. If the specified stack size is invalid, a :exc:`ValueError` is raised and the stack size is unmodified. 32kB is currently the minimum supported stack size value to guarantee sufficient diff --git a/Misc/ACKS b/Misc/ACKS --- a/Misc/ACKS +++ b/Misc/ACKS @@ -875,6 +875,7 @@ Simon Mathieu Laura Matson Graham Matthews +mattip Martin Matusiak Dieter Maurer Daniel May diff --git a/Misc/NEWS b/Misc/NEWS --- a/Misc/NEWS +++ b/Misc/NEWS @@ -163,6 +163,9 @@ Documentation ------------- +- Issue #24952: Clarify the default size argument of stack_size() in + the "threading" and "thread" modules. Patch from Mattip. + - Issue #20769: Improve reload() docs. Patch by Dorian Pula. - Issue #23589: Remove duplicate sentence from the FAQ. Patch by Yongzhi Pan. -- Repository URL: https://hg.python.org/cpython

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peps: PEP 495: Added a vertical segment to the graph.
by alexander.belopolsky Aug. 31, 2015

Aug. 31, 2015

https://hg.python.org/peps/rev/8c8352ff4668 changeset: 6024:8c8352ff4668 user: Alexander Belopolsky <alexander.belopolsky(a)gmail.com> date: Sun Aug 30 22:49:58 2015 -0400 summary: PEP 495: Added a vertical segment to the graph. files: pep-0495-fold.png | Bin pep-0495-fold.svg | 19 ++++++++++++++----- 2 files changed, 14 insertions(+), 5 deletions(-) diff --git a/pep-0495-fold.png b/pep-0495-fold.png index 7a41f601de01de65702b475c2593fc056e5e74ed..d9fe8b6eeb680cf113a3097a6c93342a418ec087 GIT binary patch [stripped] diff --git a/pep-0495-fold.svg b/pep-0495-fold.svg --- a/pep-0495-fold.svg +++ b/pep-0495-fold.svg @@ -16,7 +16,10 @@ id="svg14800" version="1.1" inkscape:version="0.91 r13725" - sodipodi:docname="pep-0495-fold.svg"> + sodipodi:docname="pep-0495-fold.svg" + inkscape:export-filename="/Users/a/Work/peps/pep-0495-fold.png" + inkscape:export-xdpi="90" + inkscape:export-ydpi="90"> <defs id="defs14802"> <marker @@ -198,7 +201,7 @@ inkscape:pageopacity="0.0" inkscape:pageshadow="2" inkscape:zoom="1.4142136" - inkscape:cx="94.546007" + inkscape:cx="93.8389" inkscape:cy="200.6291" inkscape:document-units="mm" inkscape:current-layer="layer1" @@ -330,10 +333,11 @@ inkscape:connector-curvature="0" sodipodi:nodetypes="cc" /> <path - style="fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:1;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:1, 12;stroke-dashoffset:0;stroke-opacity:1" - d="m 265.74804,680.31496 0,53.1496" + style="fill:none;fill-rule:evenodd;stroke:#336d9c;stroke-width:1;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:1, 12;stroke-dashoffset:0;stroke-opacity:1" + d="m 265.74804,680.31496 0,53.1496 z" id="path15678" - inkscape:connector-curvature="0" /> + inkscape:connector-curvature="0" + sodipodi:nodetypes="ccc" /> <path style="fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:1;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:6, 2;stroke-dashoffset:0;stroke-opacity:1" d="m 0,698.03149 248.0315,0 0,247.85676" @@ -414,5 +418,10 @@ id="tspan16460" x="343.96481" y="712.6087">Fold</tspan></text> + <path + style="fill:none;fill-rule:evenodd;stroke:#336d9c;stroke-width:2.12598425;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;stroke-miterlimit:4;stroke-dasharray:none" + d="m 265.74804,680.31492 0,53.14961" + id="path16481" + inkscape:connector-curvature="0" /> </g> </svg> -- Repository URL: https://hg.python.org/peps

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peps: PEP 495: It looks like .png should be given explicitly.
by alexander.belopolsky Aug. 31, 2015

Aug. 31, 2015

https://hg.python.org/peps/rev/0ad635b52f16 changeset: 6023:0ad635b52f16 user: Alexander Belopolsky <alexander.belopolsky(a)gmail.com> date: Sun Aug 30 22:38:20 2015 -0400 summary: PEP 495: It looks like .png should be given explicitly. files: pep-0495.txt | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/pep-0495.txt b/pep-0495.txt --- a/pep-0495.txt +++ b/pep-0495.txt @@ -93,7 +93,7 @@ this PEP specifies how various functions should behave when given an invalid instance. -.. image:: pep-0495-fold.* +.. image:: pep-0495-fold.png :align: center :width: 60% -- Repository URL: https://hg.python.org/peps

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