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* Make list comprehensions equivalent to passing a generator expression to `list()` * Reason: essentially the same and removes edge-case differences between the two * `as` a keyword [[#g 7]] * Have `True` and `False` be keywords [[#f 6]] * Reason: stop assignment to them * True division becomes default * Remove `__cmp__` (and possibly cmp() ) [[#h 8]] * Reason: TOOWTDI and rich comparisons are another way * Raise exception when comparing two heterogeneous types with operators other than `==` and `!=` * Reason: comparisons do not make sense * Automatically have types compare as not equal when types are heterogeneous [[#i 9]] * Reason: equality does not make sense between heterogeneous types * Exceptions inherit from common base class [[#j 10]] * Reason: forces use of classes as objects raised by exceptions; simplifies implementation |
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* Reorganize with more package structure * Reason: too many modules to have in a flat hierarchy |
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* Keyword for allowing shadowing of built-ins? * Prevent injecting into another modules global namespace? |
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* [[Anchor(f)]] [6] "Constancy of None" thread -- http://mail.python.org/pipermail/python-dev/2004-July/046294.html * [[Anchor(g)]] [7] " "as" to be a keyword?" thread -- http://mail.python.org/pipermail/python-dev/2004-July/046316.html * [[Anchor(h)]] [8] "lists vs. tuples" thread -- http://mail.python.org/pipermail/python-dev/2003-March/034073.html * [[Anchor(i)]] [9] another email from "lists vs. tuples" thread -- http://mail.python.org/pipermail/python-dev/2003-March/034074.html * [[Anchor(j)]] [10] "Exceptional inheritance patterns" thread -- http://mail.python.org/pipermail/python-dev/2004-August/047114.html |
This page lists features that GvR has mentioned as goals for Python 3.0. This page has been consolidated into PEP 3000; the PEP is more up-to-date and is actively maintained. #e 5
(Another list is at PythonThreeDotOh, but it incorporates items that GvR has never talked about.)
Core Language Changes
Remove distinction between int and long types. #d 4
Make all strings unicode #d 4, and have a separate bytes #b 2 type.
Replace all old-style classes. #d 4
Make the exec statement a function (again.) #a 1
Make the print statement a function. (write(x,y,z), writeln(x,y,z)) #a 1
Add a mechanism so that multiple exceptions can be caught using except E1, E2, E3:. For instance:
(Added by GvR, suggested by Bram Cohen.)Add a with statement:
Remove `x`. #a 1
Instead: use repr(x).
- Reason: backticks are hard to read in many fonts and can be mangled by typesetting software.
Remove the <> operator.
Instead: use !=.
Remove the lambda statement. #a 1 #d 4
- Instead: use a local function.
Reason: lambda supports only one statement.
Remove support for string exceptions. #a 1
- Instead: use a class.
- Perhaps have optional declarations for static typing.
One suggestion is to [http://mail.python.org/pipermail/python-dev/2004-February/042795.html use an "as" keyword for this] and for adaptation ([http://www.python.org/peps/pep-0246.html PEP 246]):
Make list comprehensions equivalent to passing a generator expression to list()
- Reason: essentially the same and removes edge-case differences between the two
as a keyword #g 7
Have True and False be keywords #f 6
- Reason: stop assignment to them
- True division becomes default
Remove __cmp__ (and possibly cmp() ) #h 8
- Reason: TOOWTDI and rich comparisons are another way
Raise exception when comparing two heterogeneous types with operators other than == and !=
- Reason: comparisons do not make sense
Automatically have types compare as not equal when types are heterogeneous #i 9
- Reason: equality does not make sense between heterogeneous types
Exceptions inherit from common base class #j 10
- Reason: forces use of classes as objects raised by exceptions; simplifies implementation
Built-In Changes
Have range(), zip(), dict.keys(), dict.items(), and dict.values() return iterators.
Move compile(), intern() and id() to the sys module. #a 1
Change max() and min() to consume iterators.
Remove coerce() as it is obsolete. #a 1
Remove dict.iteritems(), dict.iterkeys(), and dict.itervalues().
Instead: use dict.items(), dict.keys(), and dict.values() respectively.
Remove apply(). #a 1
Instead: use f(*args, **kw).
Instead: use range().
Remove map() and filter(). #a 1 #d 4
- Instead: use list comprehensions.
Remove reduce(). #a 1
- Instead: use a loop.
Remove callable(). #a 1
- Instead: catch the exception.
Instead: use new bytes type.
Remove raw_input(). #a 1
Instead: use sys.stdin.readline().
Remove input(). #a 1
Instead: use eval(sys.stdin.readline()).
Remove execfile() and reload(). #a 1
Instead: use exec().
Standard Library Changes
Remove string module. #c 4
- Instead: use string methods.
Remove other deprecated modules. #c 3
Remove sys.exc_type. #a 1
Instead: use sys.exc_info.
- Reason: it is not thread safe.
- Reorganize with more package structure
- Reason: too many modules to have in a flat hierarchy
Unresolved Issues
L += x and L.extend(x) are equivalent.
Can the parameter order of the insert method be changed so the the index parameter is optional and list.append may be removed?
Should the raise x, y syntax be removed as to favor raise x(y)?
Are repr() and str() both needed? #a 1
Should globals(), locals() and vars() be removed? #a 1
- Keyword for allowing shadowing of built-ins?
- Prevent injecting into another modules global namespace?
References
Anchor(a) [1] Python Regrets: http://www.python.org/doc/essays/ppt/regrets/PythonRegrets.pdf
Anchor(b) [2] PEP 296 -- Adding a bytes Object Type: http://python.org/peps/pep-0296.html
Anchor(c) [3] PEP 4 -- Deprecation of Standard Modules: http://python.org/peps/pep-0004.html
Anchor(d) [4] PyCon 2003 State of the Union Address: http://www.python.org/doc/essays/ppt/pycon2003/pycon2003.ppt
Anchor(e) [5] PEP 3000 -- Python 3.0 Plans: http://python.org/peps/pep-3000.html
Anchor(f) [6] "Constancy of None" thread -- http://mail.python.org/pipermail/python-dev/2004-July/046294.html
Anchor(g) [7] " "as" to be a keyword?" thread -- http://mail.python.org/pipermail/python-dev/2004-July/046316.html
Anchor(h) [8] "lists vs. tuples" thread -- http://mail.python.org/pipermail/python-dev/2003-March/034073.html
Anchor(i) [9] another email from "lists vs. tuples" thread -- http://mail.python.org/pipermail/python-dev/2003-March/034074.html
Anchor(j) [10] "Exceptional inheritance patterns" thread -- http://mail.python.org/pipermail/python-dev/2004-August/047114.html