Other syntax ideas and feature ideas for Python3.0 .

declaring parameter and variable types

It may be easier, reduce bugs, offers intelli-sense like in Microsoft Visual Studio. All of that could reduce development-time.

script to translate python source from one version to one other

does any script (will) exists, to translate code, form python 2.3 to python 2.4 or from python 2.3 to 2.4?

Different regular expressions modules for bytes and unicode text

I do not allways understand whether re module is designed for text or binary? The struct module for interfacing with binary files, or network datagrams might be improved by adding some of the regular expressions facilities, such as split.

Two modules like re might be a good thing, one binary oriented, and the other unicode oriented: * one for binary data, with some of the re and struct facilities adapted to bytes. ... with eventually stuff like reading a two bytes encoded size, then a buffer from the previous size ... * one for unicode/text regular expression should be in some way text/unicode oriented.... like ICU portable one.

For example, the ICU one provide the following patterns:

• \N{UNICODE CHARACTER NAME} Correspond au caractère nommé
• \p{UNICODE PROPERTY NAME} Correspond au carctère doté de la propriété Unicode spécifiée.
• \P{UNICODE PROPERTY NAME} Correspond au carctère non doté de la propriété Unicode spécifiée.
• \s Correspond à un caractère séparateur. un séparateur est définit comme [\t\n\f\r\p{Z}].
• \uhhhh Correspond à un caractère dont la valeur hexa est hhhh.
• \Uhhhhhhhh Correspond à un caractère dont la valeur hexa est hhhhhhhh. Exactement huit chiffres héxa doivent être fournis, même si le code point unicode le plus grand est \U0010ffff.
• the portable library "International Components for Unicode" might be used. It might be largely available as it is existing in debian distribution.

• Unicode

related pep:

• : Python Unicode Integration

• : Allow str() to return unicode strings

• : Byte vectors and String/Unicode Unification

• : Adding a bytes Object Type

New binary operator symbols d e `

these operators d e ` should be added to the language having the following meaning:

• <= >= !=

this should improve readibility (and make language more accessible to beginners).

This should be an evolution similar to the digraphe and trigraph (digramme et trigramme) from C and C++ languages. In C, "<%" or "??<" mean "{" such as.

gcc -trigraphs a.c

??=include <stdio.h>

int main(int argc, char *argv ??( ??) )
        ??<
        printf ("hello world\n");
        ??>

See also: * The <> operator: use != instead http://www.python.org/peps/pep-3000.html#id54

From an aesthetic point of view, I would very much prefer not to see the <> operator go away. At least on U.S. keyboards, you could make the case that <> is easier to type than !=, but really I just dislike the exclamation point as an operator. GIven that Python is not intended to look like C and other languages that use C-like syntax, is this really necessary? We already use "not" for logical negation rather than "!", so the argument that "!" means negation doesn't hold.

-- MichaelFromberger

Most US people will be unable to easily type ≤, ≥ or ≠ on their keyboards. I believe also that Guido has decreed ASCII as the character set with the exception of perhaps in comments and strings. Finally, what do digraphs and trigraphs have to do with your proposal? I don't think most people believe them to have been a success.

-- SkipMontanaro

For keyboard, I distinguish two issues: one is writing text (input), the other one is reading it (output/display). Most used modern systems (linux and windows) and most used modern editors (vim for example) can display unicode characters (even if some old browsers can break unicode text). For writing python, a special editor is needed due to indentations issues; such an editor might have some feature for input of some unicode characters. When not, the old system of writing a comparison with two ASCII characters '<=' is not incompatible with the use of one single unicode character ( parse can accept both). Might be the use of non ASCII (in fact, extended ASCII) characters in the source is an issue. I do not have skill for python parser. But might be nice for the long term (python 4.0?). For digraphs, I simply consider '<=' as a digraph, because the same concept can be represented with a single characer, instead of two.

Finally, some microsoft compilers are friends with extended ASCII variable names, and I believe that chinese people (those who promote international internet names) will use such programming language before 2016... --

Optional Static Typing / Adaptation

• Adding Optional Static Typing to Python - article by Guido with responses

• "Optional Static Typing" thread

• "Adding static typing to Python" thread

Lambda / Anonymous Methods / Closures

• AlternateLambdaSyntax

• Anonymous Methods / Closures

• "Securing a future for anonymous functions in Python" thread

• http://boo.codehaus.org/Closures

• http://logix.livelogix.com/tutorial/5-Standard-Logix.html#5.8 (uses same syntax as above except no multi-line support)

Print as builtin instead of a statement

• PrintAsFunction

".." Sequences, Custom Infix Operators

• http://www.livelogix.net/logix/

• "Other notes" thread

Improved default value logic for Dictionaries

• The setdefault() method is badly named and poorly designed. In a typical call, d.setdefault.(k, []).append(v), the list may be unnecessarily instantiated and discarded on every call. At a minimum, default value should be a new empty list instead of None:  d.setdefault(k).append(v) .

• A more versatile idea is to realize that defaults generalize to the whole dictionary instead of an individual lookup. A call to setdefault would then change the whole dictionary's behavior when a key is not found:

    counts = {}
    counts.setdefault(value=0)
    for elem in data:
        counts[elem] += 1

    index = {}
    index.setdefault(function=list)
    for pageno, page in enumerate(pages):
        for line in page:
            for word in line.split():
                 index[word].append(line)

Note that it's not really necessary that setdefault() take *args and **kwargs arguments to be passed to the function; PEP 309 allows a reasonable solution to this problem:

   1 from functional import partial
   2 d.setdefault(function=partial(list, [0]))
   3 d.setdefault(function=partial(dict, a=0, b=1))

Better boolean logic

The and/or operators should only return boolean values. This makes their use less error-prone, less prone to abuse, and more closely match other languages. Also, it will simplify the underlying bytecode which currently inserts many POP_TOP instructions to complete conditionals. The need to insert these instructions also results in extra code paths and jump instructions. Overall, the language will become more intuitive, more reliable, simpler, and faster.

• While I agree with your points. I would find "Better boolean logic" counter-productive in many instances. I personally prefer the former of these examples as the latter slows me down and, in my case, invites errors. {{{return a() or 'b'

#---

temp = a() if temp:

• return temp

else:

• return 'b'

}}}The latter structure always makes me shudder. I've never encountered a good use for non-boolean output from "and" (in Python. Other languages are a different story.) but using "or" in the first example is both quicker and more intuitive for many people not to mention reducing code complexity.-- StephanSokolow

Unnecessary if:else: statements to take the place of the current "or" behavior make my soul hurt. I use "and" sometimes, typically like bar = foo and foo.get('bar') when foo might be None or a dictionary. -- IanBicking

Agreed, only comparison operators (==, >, <) should return True/False, leave and/or as is (Note: the comparison operators do *not* return only True/False; they can return any value, as used by Numeric and SQLObject)

::: some new true boolean operators should be added. The binary/boolean and should be represented by one of the following: +, &&, '. The binary/boolean and should be represented by one of the following: *, ||, (.

The +, * are by mathematical analogy with addition and multiplication, within mathematical ‚ .

The && and || comes from the ugly c/java notation, I mean languages from an other century...

'. (. comes from unicode representation for boolean operations. They might be completed by three others boolean operators, xor, nand and nor: » ¼½ '. ( are for boolean what )* are for set. (similar notation, similar meaning).

They also have a curly notation: ÎÏ.

a + b # a or b. should return True, when a and b are true (instead of 2) 
a * b #should return a logic_and b for boolean

a && b #should return a logic_and b for boolean
a || b #should return a logic_or b for boolean

a ' b #should return a logic_and b 
a ( b #should return a logic_or b 

should return True or False

Disallow calling class methods from instances

Calling with a instance is almost never what you want. When it is done, the results are not especially readable, and the code suggests that it is doing something that it isn't:

{'a'=1}.fromkeys('poof') # what happened to 'a'? 

I disagree to this. Although calling class methods on the instance from the outside will usually be rubbish, it will very often be useful and intended behavour inside instances. For example:

class mydict(dict):
  def key_copy(self):
    return self.fromkeys(self)    

This will assert that whatever subclass of mydict is created and not some other class. One could argue though that this could be achieved by the more cluttersome self.__class__.fromkeys().

Simplify the syntax for raising exceptions

• Eliminate string exceptions entirely.

• Alway require instantation. IOW, prefer raise ValueError(dat) to raise ValueError, dat.

• Require that all exceptions subclass from Exception.

• Have Exception be a new-style class

Include docstrings when printing user-defined exceptions such as implemented by http://soiland.no/software/doc_exception.py:

>>> class IdiotError(Exception):
...    """Some idiot occured"""
...
>>> raise IdiotError
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
__main__.IdiotError: Some idiot occured

This could simply be implemented in Exception.__str__ when args is empty.

Fix implementation of in-place operators

The current implementation will call __iadd__(), allowing it to do the in-place change, but then require that the method return the new value and then store it again. Ideally, all the responsibility for the update should lie with the __iadd__() method and it should return None. This simplifies the bytecode and eliminates some annoying behavior (such as a[0]+=1 succeeding and raising an error when a=([0],).

Remove the distinction between data and non-data decriptors

Having the distinction provides a tiny benefit but incurs a large cost in terms of implementation complexity and increasing the learning curve for descriptors. Using the presence or absence of a setter to distinquish the two is somewhat hackish and confuses the heck out of anyone first trying to master descriptors. Even after using descriptors for a while, that nuance remains an annoying distraction.

Note that descriptors are a somewhat advanced feature, not really expected to be used by beginners or on a day to day basis, so the extra flexibilty given by by the data/non-data descriptors distinction may still be worth the small extra complexity it adds to the protocol .

Reconsider the inclusion of __slots__ or re-evaluate its implementation

Guido has expressed that this is a highly popular, but badly misunderstood tool that is often used incorrectly.

• If __slots__ is misspelled, there is no visible indication of failure.

• The purpose of the tool is not to make it more difficult to assign attributes.

• __slots__ do not inherit.

• __slots__ complicates and slows the implementation of new-style classes.

I have never see __slots__ misused, or used much at all, so maybe in typical real projects misuse isn't much of an issue? -- IanBicking

Extra operators for strings and lists

Operators as - & | ^ should be used for strings and lists directly in place of first making a set data type (see PEP 218 - Adding a Built-In Set Object Type).

The operators /, * and % could also be used to split and stitch strings and lists:

   1 # split:
   2 'spameggsham' / 'a' == 'spameggsham'.split('a') == ['sp', 'meggsh', 'm']
   3 # remainder:
   4 'spameggsham' % 'a' == 'aa'
   5 # stitch:
   6 ['sp', 'meggsh', 'm'] * 'a' == 'spameggsham'
   7 
   8 # split list:
   9 [1, 2, 3, 4, 5] / [2, 3] == [[1], [4, 5]]

• 'spameggsham' % 'a' == 'aa' is sort of unclear, and .count('a') works just as well. The others sound fine.-- ChrisRebert

Move rarely-used builtins to the library

pow() to the math module!

Don't remove callable()

Please don't. There are times where you want to know if an object is callable without calling it. For instance if you create a metaclass and need to wrap defined methods passed to __new__, and don't want to wrap class variables.

• Why use callable() then? Isn't this what inspect.ismethod(), .isfunction() etc. are for? --StevenBethard

In addition, using exceptions for normal control flow is not good code style.

• Using exceptions in normal control flow is very typical in Python code, so not everyone agrees -- IanBicking

Make API of set, list, dict more consistent

No need for copy function. A clear function for all of them.

Make copy and deepcopy built-ins, replace copy methods by __copy__

It would clarify how copy should be done.

• Some people will argue that copy is hard, and deepcopy nearly impossible, to do "right" for a typical program, and so you shouldn't encourage these to be used generally. For specific data types -- like dictionaries and lists -- there are simple idioms for copies. -- IanBicking

Don't remove cmp() and __cmp__

Even if it looks as if "there's more than one way to do it" applies, it makes implementing comparison so easy that it must be kept. If the rule "there's only one way to do it" is important, maybe only keep cmp?

   1    def __cmp__(self, other):
   2       return cmp(self.member1, other.member1) or cmp(self.member2, other.member2)

Are rich comparisons really that much more complex?

   1    def __lt__(self, other):
   2       return (self.member1, other.member1) < (self.member2, other.member2)

Builtin Literal for sets

Make a set literal:

   1    # Use "< >"
   2    s = <'a', 'b', 'c'>
   3    
   4    # Or use "| |"
   5    s = |'a', 'b', 'c