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Hello IronPython Community,

I’m pleased to announce IronPython 2.0 Beta 1. This particular release contains almost one hundred bug fixes of which the majority were reported on CodePlex (118 votes)! 2.0 Beta 1 includes the following improvements over the Alphas:
  • PEP 328, absolute and relative imports, has been implemented
  • PEP 302, new import hooks, has been implemented
  • Numerous Python dictionary improvements
  • ‘sys’ is now a real builtin module
  • Test projects for IronPython .NET (ClrAssembly) and COM interop (DlrComLibrary) support have been added to the ‘Src\Tests’ directory within the source zip file
  • More improvements to the –X:PreferComDispatch flag

The following CodePlex Work Items have been closed since IronPython 2.0 Alpha 8:
  • 946 import clr doesn't give access to the contents of builtins using .NET method names
  • 1402 try-finally has an issue in generator
  • 2206 with statement broken in command line
  • 2443 problem with slots and init in new-style classes
  • 2648 Error importing module
  • 2704 import and packages aren't mixing well
  • 3092 struct.unpack mishandling the "x" format code
  • 3117 dict.update doesn't take keyword arguments - differs from CPython
  • 3287 Descriptor/metaclass problems
  • 4197 Trivial: int('0x20', 16) fails to parse, long too
  • 4322 unpacking single element tuples in for-statement, listcomp and generator
  • 4691 AttributeError on ComObject when using a C++/ATL/MFC COM object which implements a .NET interface
  • 5083 operator.contains is broken
  • 5447 socket.getnameinfo(...) broken under Vista
  • 5566 base64 slash bug
  • 5609 Trivial: Python25: File lacks enter and exit
  • 5801 Class with slots and getattr not compatible
  • 5904 Trivial: Multi-line dictionary/list/tuple expressions in IP interpreter console not compatible w/ CPython Interpreter console
  • 6006 pyc is mixing up ia64 and x64
  • 6265 maxsplit keyword arg of re.split not accepted
  • 6272 re.compile(...).match(...).endpos has an incorrect value
  • 6805 Trivial: funccode.coargcount and funccode.coflags are wrong
  • 6991 Trivial: IDictionary.GetEnumerator on IronPython Dict returns the wrong enumerator implementation
  • 7972 if the argument k in method GetRandBits(k) is not greater than zero, the valueError would be thrown
  • 8009 the getrandbits method would throw overflow exception in ironpython if the argument k is a int.MaxValue
  • 8297 range w/ large negative number produces incorrect results
  • 8361 Trivial: popen shouldn't open new window
  • 8678 itertools.izip does not work when the arguments are the same iterator
  • 8780 Removes the inexistent file did not throw OSError in IP
  • 9070 Python25: Assertions Fail with unittest - requires 2.5 style exceptions
  • 9349 The array.array format "I" handles large values incorrectly
  • 9351 int() doesn't convert representable longs to int
  • 10291 calling base class call invokes constructor instead
  • 10577 Trivial: Python25: Attempts to set dict of new style classes fails with wrong exception WRT CPython 2.5
  • 10642 Non-empty expression list after "yield" keyword gives a SyntaxError
  • 10643 Can't assign to []
  • 10648 Trivial: rpartition method of string objects broken when no separator match is found
  • 10709 Using lambda in class definition will add <lambda$..> into the class's dictionary
  • 10782 Python25: Stringified representation of exception classes are incorrect
  • 10983 Reading files in text mode reads chars > 0x7F as '?'
  • 11362 Tracebacks not generated under 64-bit OSes
  • 11487 str does not call repr in new style classes
  • 11576 SystemError: Ambiguous match found.
  • 11760 Method incorrectly casts to PythonFunction.
  • 12038 Parser reports weird SyntaxError when trying to use digits for member names
  • 12493 Error in import
  • 12647 Implement coerce, float, index, long, and rdivmod for bool type
  • 13617 Trivial: Modules with bad encoding names throw wrong exception
  • 13618 IRONPYTHONPATH should be split with platform-specific path separator
  • 13651 importing package with imp module
  • 13686 Using setattr with modules
  • 13806 Cannot import Python 2.5 email module
  • 13860 Complex infinite not allowed by IP
  • 14454 Event handlers can cause circular references and leak memory
  • 14456 raw_input blocks until 20 characters are read
  • 14499 Trivial: sys.version incorrect in IP2.0A7
  • 14539 .Visible=True (property) does not work in 2.0
  • 14605 Trivial: Enum truth broken
  • 14636 Trivial: Bug in ScriptDomainManager.GetPublishedModules()
  • 14833 Remove -X:AssembliesDir flag
  • 14861 Value types don't work when a function is called twice
  • 14878 type(sys) does not have a default constructor
  • 14882 Trivial: Implement
  • 14982 Trivial: able to derive from System.Double (or not able to derive from System.Single)
  • 15102 Deriving from "property" breaks default constructor params
  • 15289 re module never compiles regular expressions

We’d like to think everyone in the IronPython Community who reported these: undebtedly, Anthony Baxter, pobrien, Kamil Dworakowski, millind, romank, tarlano, Michael Foord, Evan Klitzke, sanxiyn, jbevain, jackeyoo, Jeff Brown, Oliver Yu, rridge, lthompson, JiaJun Liu, CriGoT, abs, jdhardy, sbergman, sjmachin, Eloff, atifaziz, arman0, Qvin, Vizcayno, Davy Mitchell, CurtHagenlocher, Laurion, luntain, py_sunil, zvikag, David Fraser, Gary Stephenson, and Beaton.

Additionally, we’ve closed the following bugs that were reported internally:
  • 12% perf degrade on worst case generator scenario with loops
  • Copying arguments for the ContextAware methods in BuiltinFunction.cs
  • Performance issues in the Dict implementation
  • Trivial: overhead in using typed slots with environment
  • PythonFile.Write flushes on each write
  • Document difference converting instance without complex or float to complex
  • IronPython: Cannot step into a method
  • IronPython: Cannot Localize Windows Forms
  • formatting with '%o' on object which has oct defined
  • 6% degrade in the try-raise-except scenario by change#183362
  • unicode() can't handle 'unicode-escape'
  • raw_input is broken
  • it is different for yield statement between IronPython and CPython .
  • ImportError: Cannot import name defaultdict
  • true division(from future import division) throws OverflowError on division by huge number
  • tuple(0,1,2,3,4)-100:100:-1 throw OverflowError
  • a derived tuple which overrode the method getitem gets an error result with the iter()
  • Trivial: u''.isdecimal() returns 'True' in IronPython but 'False' in CPython
  • there are different handle for getweakrefs and refequal against IronPython and CPython. lead to different result
  • istitle() returns False in IronPython with unicode object from u'\u1F88' to u'\u1FFc'
  • PythonContext.DisplayName is broken
  • return can't have an expression in generators
  • expect System.Nullable() returning the non-generic type, instead TypeError thrown
  • Dict slice eval order is incorrect
  • ctime() returns unicode on non-English machine
  • Can't call old style classes with non-simple signatures when init is not defined
  • with doesn’t work in interactive mode.
  • One overload is missing for decode methods in _codecs module.

You can download IronPython 2.0 Beta 1 at:

The IronPython Team


The hosting APIs are nearing completion and will be unlikely to change much in future IronPython 2.0 releases. For anyone interested, you might want to check out “EngineTest.cs” and “” in the source zip file to get an idea of where the hosting APIs are for Beta 1. It’s also worth pointing out that the ‘CodeBlock’/’CodeBlockInfo’ AST symbols have been renamed to ‘LambdaExpression’ and ‘LambdaInfo’ respectively. The APIs around both of these changed significantly since the last release.

ToyScript, a small scripting language built on top of the DLR, is merely a DLR sample and not some new scripting language Microsoft has created. Also, ToyScript is not intended to be distributed with IronPython on a permanent basis.

Last edited Mar 13, 2008 at 12:34 AM by dfugate, version 1


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