3ddcf63821
git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@2508 fd906abe-77d9-0310-91a1-e0d9ade77398
135 lines
3.2 KiB
Text
135 lines
3.2 KiB
Text
==============================================
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Python Execution in Special Dynamic Namespaces
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==============================================
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$Id$
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>>> from cybertools.util import namespace
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A Very Restricted Basic Namespace
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=================================
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>>> minimal = namespace.BaseNamespace()
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We
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>>> code = """
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... print 'Hello'
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... # a comment
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... print dir('')
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... print '__builtins__:', __builtins__
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... output('something')
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... a = 'a is a variable'
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... if a:
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... print a
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... """
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>>> exec code in minimal
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Hello
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['__add__', ..., 'zfill']
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__builtins__: {}
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something
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a is a variable
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Assignments in code executed in a namespace may be accessed as attributes
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of the namespace later.
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>>> minimal.a
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'a is a variable'
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By setting the ``__builtins__`` mapping to an empty dictionary the minimal
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namespace provides a secure restricted execution environment.
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>>> exec "import os" in minimal
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Traceback (most recent call last):
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...
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ImportError: __import__ not found
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>>> exec "f = open('dummy.txt', 'w')" in minimal
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Traceback (most recent call last):
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...
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NameError: open
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Elements and sub-elements
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-------------------------
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>>> code = """
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... topic('zope3', title='Zope 3')[
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... annotation(author='jim')]
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... topic('python')[
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... annotation(author='guido'),
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... child('zope3')]
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... """
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>>> from cybertools.util.jeep import Jeep
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>>> topics = Jeep()
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>>> symbols = namespace.BaseNamespace()
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>>> symbols['topic'] = namespace.Element(symbols, 'topic', topics)
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>>> symbols['annotation'] = namespace.Element(symbols, 'annotation')
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>>> symbols['child'] = namespace.Element(symbols, 'child')
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>>> exec code in symbols
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>>> dict(topics)
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{'python': <Element 'python'>, 'zope3': <Element 'zope3'>}
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>>> dict(topics['python'].subElements)
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{'zope3': <Element 'zope3'>, 'annotation': <Element 'annotation'>}
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A Namespace Automatically Generating Elements
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=============================================
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>>> auto = namespace.AutoNamespace()
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>>> exec "print something" in auto
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something
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>>> auto.something
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<Element 'something'>
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Execution of Python Code in a Namespace
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=======================================
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To simplify some standard use cases for working with namespaces the
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module provides two classes for execution of Python code with appropriate
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simple error handling.
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Evaluation of Python expressions
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--------------------------------
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When evaluating an expression we always get a pair with the resulting
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value and an - hopefully empty - error string.
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>>> ev = namespace.Evaluator(auto)
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>>> ev.evaluate('25 * 25')
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(625, '')
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>>> ev.evaluate('30/0')
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(None, 'Traceback...ZeroDivisionError...')
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Trying to execute a statement leads to a syntax error.
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>>> ev.evaluate('print something_else')
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(None, 'Traceback...SyntaxError...')
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But we can explicitly allow the execution of statements. The result
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of executing a statement is None.
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>>> ev = namespace.Evaluator(auto, allowExec=True)
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>>> ev.evaluate('print something_else')
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something_else
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(None, '')
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>>> ev.evaluate('25 * 25')
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(625, '')
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Execution of Statements
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-----------------------
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>>> ex = namespace.Executor(auto)
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>>> ex.execute('number = 25')
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''
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>>> ex.execute('30/0')
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'Traceback...ZeroDivisionError...'
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