Current File : //proc/self/root/opt/alt/python27/lib64/python2.7/site-packages/sqlalchemy/sql/visitors.pyo
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e f d � � YZ d e f d � � YZ d � Z d � Z d � Z d � Z d � Z d � Z d � Z d S( sO Visitor/traversal interface and library functions.
SQLAlchemy schema and expression constructs rely on a Python-centric
version of the classic "visitor" pattern as the primary way in which
they apply functionality. The most common use of this pattern
is statement compilation, where individual expression classes match
up to rendering methods that produce a string result. Beyond this,
the visitor system is also used to inspect expressions for various
information and patterns, as well as for usage in
some kinds of expression transformation. Other kinds of transformation
use a non-visitor traversal system.
For many examples of how the visit system is used, see the
sqlalchemy.sql.util and the sqlalchemy.sql.compiler modules.
For an introduction to clause adaption, see
http://techspot.zzzeek.org/2008/01/23/expression-transformations/
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VisitableTypet Visitablet
ClauseVisitort CloningVisitort ReplacingCloningVisitort iteratet iterate_depthfirstt traverse_usingt traverset traverse_depthfirstt cloned_traverset replacement_traversec B s e Z d Z d � Z RS( se Metaclass which assigns a `_compiler_dispatch` method to classes
having a `__visit_name__` attribute.
The _compiler_dispatch attribute becomes an instance method which
looks approximately like the following::
def _compiler_dispatch (self, visitor, **kw):
'''Look for an attribute named "visit_" + self.__visit_name__
on the visitor, and call it with the same kw params.'''
visit_attr = 'visit_%s' % self.__visit_name__
return getattr(visitor, visit_attr)(self, **kw)
Classes having no __visit_name__ attribute will remain unaffected.
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for use by the compiler.
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visit_nameR" ( ( R R! sJ /opt/alt/python27/lib64/python2.7/site-packages/sqlalchemy/sql/visitors.pyR I s c B s e Z d Z RS( sT Base class for visitable objects, applies the
``VisitableType`` metaclass.
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d � � Z d � Z RS( sZ Base class for visitor objects which can traverse using
the traverse() function.
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Wd S( Ns visit_%s( t visitor_iteratorR# R t None( R t objR t vR ( ( sJ /opt/alt/python27/lib64/python2.7/site-packages/sqlalchemy/sql/visitors.pyt traverse_single s c C s t | | j � S( sa traverse the given expression structure, returning an iterator
of all elements.
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c c s. | } x! | r) | Vt | d d � } q Wd S( s8 iterate through this visitor and each 'chained' visitor.t _nextN( R# R, ( R R. ( ( sJ /opt/alt/python27/lib64/python2.7/site-packages/sqlalchemy/sql/visitors.pyR+ � s c C s t | j � d } | | _ | S( s� 'chain' an additional ClauseVisitor onto this ClauseVisitor.
the chained visitor will receive all visit events after this one.
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the cloned_traverse() function.
c C s g | D] } | j | � ^ q S( s` Apply cloned traversal to the given list of elements, and return
the new list.
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the replacement_traverse() function.
c C s d S( s receive pre-copied elements during a cloning traversal.
If the method returns a new element, the element is used
instead of creating a simple copy of the element. Traversal
will halt on the newly returned element if it is re-encountered.
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traversal is configured to be breadth-first.
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traversal is configured to be depth-first.
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objects.
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