diff options
Diffstat (limited to 'examples/elementtree/adjacency_list.py')
| -rw-r--r-- | examples/elementtree/adjacency_list.py | 83 |
1 files changed, 49 insertions, 34 deletions
diff --git a/examples/elementtree/adjacency_list.py b/examples/elementtree/adjacency_list.py index 1f7161212..6dd88c797 100644 --- a/examples/elementtree/adjacency_list.py +++ b/examples/elementtree/adjacency_list.py @@ -1,4 +1,6 @@ -"""Illustrates an explicit way to persist an XML document expressed using ElementTree. +""" +Illustrates an explicit way to persist an XML document expressed using +ElementTree. Each DOM node is stored in an individual table row, with attributes represented in a separate table. The @@ -8,34 +10,37 @@ along any path with a given structure of attributes, basically a (very narrow) subset of xpath. This example explicitly marshals/unmarshals the ElementTree document into -mapped entities which have their own tables. Compare to pickle.py which -uses pickle to accomplish the same task. Note that the usage of both -styles of persistence are identical, as is the structure of the main Document class. +mapped entities which have their own tables. Compare to pickle.py which uses +pickle to accomplish the same task. Note that the usage of both styles of +persistence are identical, as is the structure of the main Document class. """ -################################# PART I - Imports/Coniguration #################################### -from sqlalchemy import ( - MetaData, - Table, - Column, - Integer, - String, - ForeignKey, - Unicode, - and_, - create_engine, -) -from sqlalchemy.orm import mapper, relationship, Session, lazyload +# PART I - Imports/Configuration +import io +import os +import re +from xml.etree import ElementTree -import sys, os, io, re +from sqlalchemy import and_ +from sqlalchemy import Column +from sqlalchemy import create_engine +from sqlalchemy import ForeignKey +from sqlalchemy import Integer +from sqlalchemy import MetaData +from sqlalchemy import String +from sqlalchemy import Table +from sqlalchemy import Unicode +from sqlalchemy.orm import lazyload +from sqlalchemy.orm import mapper +from sqlalchemy.orm import relationship +from sqlalchemy.orm import Session -from xml.etree import ElementTree e = create_engine("sqlite://") meta = MetaData() -################################# PART II - Table Metadata ######################################### +# PART II - Table Metadata # stores a top level record of an XML document. documents = Table( @@ -75,10 +80,12 @@ attributes = Table( meta.create_all(e) -#################################### PART III - Model ############################################# +# PART III - Model # our document class. contains a string name, # and the ElementTree root element. + + class Document(object): def __init__(self, name, element): self.filename = name @@ -90,19 +97,22 @@ class Document(object): return buf.getvalue() -#################################### PART IV - Persistence Mapping ################################# +# PART IV - Persistence Mapping + +# Node class. a non-public class which will represent the DB-persisted +# Element/SubElement object. We cannot create mappers for ElementTree elements +# directly because they are at the very least not new-style classes, and also +# may be backed by native implementations. so here we construct an adapter. + -# Node class. a non-public class which will represent -# the DB-persisted Element/SubElement object. We cannot create mappers for -# ElementTree elements directly because they are at the very least not new-style -# classes, and also may be backed by native implementations. -# so here we construct an adapter. class _Node(object): pass -# Attribute class. also internal, this will represent the key/value attributes stored for -# a particular Node. +# Attribute class. also internal, this will represent the key/value attributes +# stored for a particular Node. + + class _Attribute(object): def __init__(self, name, value): self.name = name @@ -130,9 +140,12 @@ mapper( mapper(_Attribute, attributes) -# define marshalling functions that convert from _Node/_Attribute to/from ElementTree objects. -# this will set the ElementTree element as "document._element", and append the root _Node -# object to the "_root" mapped collection. +# define marshalling functions that convert from _Node/_Attribute to/from +# ElementTree objects. this will set the ElementTree element as +# "document._element", and append the root _Node object to the "_root" mapped +# collection. + + class ElementTreeMarshal(object): def __get__(self, document, owner): if document is None: @@ -180,7 +193,7 @@ class ElementTreeMarshal(object): # override Document's "element" attribute with the marshaller. Document.element = ElementTreeMarshal() -########################################### PART V - Basic Persistence Example ##################### +# PART V - Basic Persistence Example line = "\n--------------------------------------------------------" @@ -202,7 +215,7 @@ document = session.query(Document).filter_by(filename="test.xml").first() print(document) -############################################ PART VI - Searching for Paths ######################### +# PART VI - Searching for Paths # manually search for a document which contains "/somefile/header/field1:hi" d = ( @@ -218,6 +231,8 @@ d = ( print(d) # generalize the above approach into an extremely impoverished xpath function: + + def find_document(path, compareto): j = documents prev_elements = None |