Source code for qal.dataset.xpath

Created on Sep 14, 2012

@author: Nicklas Boerjesson

import io
from qal.common.strings import make_path_absolute

from qal.dataset.custom import CustomDataset
from qal.common.listhelper import find_next_match, find_previous_match
from lxml import _elementpath
from lxml import etree
from lxml.etree import SubElement

[docs]def xpath_data_formats(): return ["XML", "XHTML", "HTML"] # "UNTIDY_HTML"]
[docs]class XpathDataset(CustomDataset): """This class implements data formats that are possible to query via XPath. Currently XML and HTML are implemented(XHTML isn't tested). Untidy HTML will be implemented using the Beautiful Soup library. """ filename = None """The name of the file to be loaded""" rows_xpath = None """The XPath to the "row" nodes of the data set. Ex: /books/book""" field_xpaths = None """A list of XPaths relative to the rows_xpath leading to each field. Ex: ["title", "id"]""" xpath_data_format = None """The data format. Can be either "XML", "XHTML" or "HTML".""" _structure_tree = None """A private reference to the node tree, when load is called with _add_node_ref=True, an instance is kept for more efficient merging with diff data""" _structure_row_node_parent = None """A private reference to the parent node of the row nodes in the structure """ _structure_key_fields = None """A private list of key fields.""" _structure_row_node_name = None """ A private variable holding the tag name of the row node. .. todo:: Should this be able to hold an XML? """ _structure_top_node = None """ A private variable holding the top node of the structure. """ def __init__(self, _filename = None, _rows_xpath = None, _resource = None): """Constructor. :param str _filename: Name of the file to parser :param str _rows_xpath: Path to nodes holding the rows. :param Resource _resource : An instance of a :py:class: qal.common.resource.resource """ super(XpathDataset, self ).__init__() self.field_xpaths = [] self._structure_key_fields = [] if _resource: self.read_resource_settings(_resource) else: if _filename != None: self.filename = _filename else: self.filename = None if _rows_xpath != None: self.rows_xpath = _rows_xpath else: self.rows_xpath = None
[docs] def read_resource_settings(self, _resource): """Reads settings from a resource""" self._base_path = _resource.base_path if _resource.type.upper() != 'XPATH': raise Exception("XpathDataset.read_resource_settings.parse_resource error: Wrong resource type: " + _resource.type) self.filename ="filename") self.rows_xpath ="rows_xpath") self.xpath_data_format ="xpath_data_format") self.field_names ="field_names") self.field_xpaths ="field_xpaths") self.field_types ="field_types") self.xpath_text_qualifier ="xpath_text_qualifier") self.encoding ="encoding")
[docs] def write_resource_settings(self, _resource): """Write settings to a resource""" _resource.type = 'XPATH'["filename"] = self.filename["rows_xpath"] = self.rows_xpath["xpath_data_format"] = self.xpath_data_format["field_names"] = self.field_names["field_xpaths"] = self.field_xpaths["field_types"] = self.field_types["xpath_text_qualifier"] = self.xpath_text_qualifier["encoding"] = self.encoding
def _file_to_tree(self, _data_format, _reference): """Reads a file and chooses the right parser to make it an lxml element tree""" print("format_to_tree : " + _data_format) if _data_format == 'HTML': from lxml import html return html.parse(_reference) if _data_format == 'XML': from lxml import etree return etree.parse(_reference) else: raise Exception("_file_to_tree: " + _data_format + " is not supported") def _structure_parse_qal_xpath(self, _qal_xpath): """Parse the trailing attribute identifier from the QAL xpath string. ":" isn't allowed in xpath. :param str _qal_xpath: QAL xpath string. Ex. "library/books/book | library/books" """ _parts = _qal_xpath.split("::") if len(_parts) == 2: return _parts[0], _parts[1] else: return _qal_xpath, None
[docs] def load(self, _add_node_ref = None): """Parse file, apply root XPath to iterate over and then collect field data via field_xpaths. :param bool add_node_ref: If set, add an extra column with references to the underlying XML nodes, \ used to efficiently apply new data. """ print("Loading : " + self.filename) self.log_load(self.filename) try: _tree = self._file_to_tree(self.xpath_data_format, make_path_absolute(self.filename, self._base_path)) except Exception as e: raise Exception("XpathDataset.load - error parsing " + self.xpath_data_format + " file : " + str(e)) #_root_nodes = _tree.xpath("/html/body/form/table/tr[4]/td[2]/table/tr[2]/td/table[2]/tr/td/table/tr[10]/td/table/tr") _root_nodes = _tree.xpath(self.rows_xpath) if len(_root_nodes) > 0: self._structure_tree = _tree self._structure_row_node_parent = _root_nodes[0].getparent() self._structure_top_node = _tree.getroot() _data = [] if self.field_xpaths is not None and len(self.field_xpaths) > 0: for _curr_row in _root_nodes: _row_data = [] for _field_idx in range(0, len(self.field_names)): _curr_path, _curr_attribute = self._structure_parse_qal_xpath(self.field_xpaths[_field_idx]) if _curr_path != "": _found_node = _curr_row.xpath(_curr_path) if len(_found_node)>0: _item_data = _found_node[0] else: _item_data = None else: _item_data = _curr_row if _item_data is not None: if _curr_attribute: if _curr_attribute[0] == "@": _row_data.append(self.cast_text_to_type(_item_data.get(_curr_attribute[1:]), _field_idx)) elif _curr_attribute.lower() == "xml": _row_data.append(self.cast_text_to_type(_item_data.tostring(), _field_idx)) else: raise Exception("Param_XPath.load: Error, attribute references must have the ::@AttributeName- format or ::XML. The attribute was \""+_curr_attribute + "\"") else: _row_data.append(self.cast_text_to_type(_item_data.text, _field_idx)) else: _row_data.append("") # Add reference to XML structure. if _add_node_ref: _row_data.append(_curr_row) print(str(_row_data)) _data.append(_row_data) self.data_table = _data return _data
def _structure_create_xpath_nodes(self, _node, _xpath): """Used an xpath to create nodes that match the path and its conditions(names, attributes and so forth)""" print("_create_xpath_nodes: " + str(_xpath)) _curr_node = _node # Break up the string in its tokens _tokens = list(_elementpath.xpath_tokenizer(_xpath)) print(str(_tokens)) # Iterate through tokens, until we have gone through the entire XPath. _token_idx = 0 # But first, move past any root reference and conditions. # TODO: This is a bit ugly, perhaps. if len(_tokens) > 1 and (_tokens[0][0] == "/") and (_tokens[1][1] == _node.tag): print("_create_xpath_nodes: Ignoring root node path and condition.") _token_idx+=1 while _token_idx < len(_tokens) and _tokens[_token_idx][0] != "/": _token_idx+=1 while _token_idx < len(_tokens): print("_tokens[" + str(_token_idx) + "][0]:" + str(_tokens[_token_idx][0])) #Is this a new level? if _tokens[_token_idx][0] == "/": # Then the next is the name of the node _token_idx+=1 if _tokens[_token_idx][0] == "": _next_name = _tokens[_token_idx][1] #Is the next token a condition? if _token_idx + 1 < len(_tokens) and _tokens[_token_idx + 1][0] == "[" : #It was, move on _token_idx+=1 #Find ending of condition _end_cond_idx = self.find_next_match(_tokens, _token_idx, ("]","")) if _end_cond_idx == -1: raise Exception("_create_xpath_nodes: Cannot find end of condition.\nXPath = " + _xpath) #Create relative path _check_path = "".join((_a[0]+_a[1] for _a in _tokens[_token_idx -1:_end_cond_idx + 1])) #Then check if it exists print("_check_path:" + str(_check_path)) _found_nodes = _curr_node.xpath(_check_path) # Node found, move on if _found_nodes and len(_found_nodes) == 1: _token_idx+=1 _curr_node = _found_nodes[0] else: # If not found create node print("add node: " + str(_next_name)) _curr_node = SubElement(_curr_node, _next_name) # If they can be discerned(@id=value), add attributes if _tokens[_token_idx + 3][0] == "=" and _tokens[_token_idx + 1][0] == "@": print("set attribute to satisfy this path: " + str(_check_path)) _curr_node.set(_tokens[_token_idx + 2][1], str(_tokens[_token_idx + 4][0]).strip("\"'")) _token_idx+=5 else: if isinstance(_curr_node, str): raise Exception("_structure_create_xpath_nodes - Internal error: Node is a string, missing node ref, was _add_node_ref used? \nData :" + _curr_node+" | "+_next_name+" | "+_xpath+" | "+str(_tokens)) _found_nodes = _curr_node.xpath(_next_name) # Node found, move on if len(_found_nodes) == 1: _curr_node = _found_nodes[0] else: print("Create new node: " + str(_next_name)) _curr_node = SubElement(_curr_node, _next_name) _token_idx+=1 return _curr_node def _structure_parse_root_path(self, _root_path): """Extract information from the root path to get sufficient information for specifying the destination and creating new nodes. \n * If many XPaths in the string, it uses the first one * Parses the root node name * Parses the row parent node path * Parses the row node name""" if _root_path == "": raise Exception("_parse_root_path: Root path cannot be empty") # Parse XPath tokens _root_xpath_tokens = list(_elementpath.xpath_tokenizer(self.rows_xpath)) # Use only first path for destination try: _first_splitter = _root_xpath_tokens.index(('', '|')) print("_parse_root_path: Multiple XPaths, using first.") _split_xpath = "".join((_a[0]+_a[1] for _a in _root_xpath_tokens[0:_first_splitter])) except ValueError: _split_xpath = self.rows_xpath # Get the root node name if _root_xpath_tokens[0][0] == "/": _root_node_name = _root_xpath_tokens[1][1] else: raise Exception("_parse_root_path: It is necessary to have an absolute (\"/node\") top node name in the XPath") print("_root_node_name=" + str(_root_node_name)) # Get the row node name _row_node_name_idx = find_previous_match(_root_xpath_tokens, len(_root_xpath_tokens) -1, ("/", "")) if _row_node_name_idx == -1: raise Exception("_parse_root_path: Cannot find start of condition.\nXPath = " + _root_path) else: _row_node_name = _root_xpath_tokens[_row_node_name_idx + 1][1] if _row_node_name_idx == 0: raise Exception("_parse_root_path: The row node cannot be the root node.\nXPath = " + _root_path) print("_structure_row_node_name=" + str(_row_node_name)) # Move on backward, what's left is the path to the parent of the row node, we need it to be able # to create rows, as the path may not return a node to find a parent from _row_node_parent_xpath = "".join((_a[0]+_a[1] for _a in _root_xpath_tokens[0:_row_node_name_idx])) print("_row_node_parent_xpath=" + str(_row_node_parent_xpath)) return _root_node_name, _row_node_name, _row_node_parent_xpath def _structure_init(self, _dataset): """Initializes the XML structure that data is to be applied to.""" print("XpathDataset._structure_init") super(XpathDataset, self)._structure_init(_dataset) # Parse important information data from XPath _root_node_name, self._structure_row_node_name, _parent_xpath = self._structure_parse_root_path(self.rows_xpath) # If the structure already loaded? if self._structure_row_node_parent is None: # If not try to load, or create file. import os if os.path.exists(make_path_absolute(self.filename, self._base_path)): try: self.load(_add_node_ref=True) except Exception as e: raise Exception(" - error parsing " + self.xpath_data_format + " file : " + str(e)) else: # Create a tree with root node based on the first if _root_node_name != "": if self.encoding: _encoding = self.encoding else: _encoding = "UTF-8" _tree = etree.parse(io.StringIO("<?xml version='1.0' ?>\n<" + _root_node_name + "/>")) else: raise Exception(" - rows_xpath("+ str(self.rows_xpath)+") must be absolute and have at least the name of the root node. Example: \"/root_node\" ") # If the structure there yet? It could be an XML file with only a top node. if self._structure_row_node_parent is None: # If not existing, create a node structure up to the parent or the row nodes # from the information in the xpath. self._structure_top_node = self._structure_create_xpath_nodes(self._structure_top_node, self.rows_xpath) def _structure_populate_row(self, _node, _row_data): for _field_idx in range(len(self.field_xpaths)): _curr_path, _curr_attribute = self._structure_parse_qal_xpath(self.field_xpaths[_field_idx]) _curr_node = self._structure_create_xpath_nodes(_node, _curr_path) _new_value = str(_row_data[_field_idx]) print("_curr_path :" + str(_curr_path)) print("_curr_attribute :" + str(_curr_attribute)) print("_new_value :" + str(_new_value)) #TODO: Support XML? if _curr_attribute: _curr_node.set(_curr_attribute[1:], _new_value) else: _curr_node.text = _new_value def _structure_insert_row(self, _row_idx, _row_data, _commit=True, _no_logging=None): if _commit is True: """Override parent to add XML handling""" # Last column is a reference print("_row_data: " + str(_row_data)) _last_row_idx = len(self.data_table) -1 if _row_idx > _last_row_idx: _row_node = self.data_table[_last_row_idx][len(self.data_table[_last_row_idx]) -1] else: _row_node = self.data_table[_row_idx][len(self.data_table[_row_idx]) -1] _new_element = etree.Element(self._structure_row_node_name) # Insert row node self._structure_row_node_parent.insert(_row_idx, _new_element) self._structure_populate_row(_new_element, _row_data) # Call parent super(XpathDataset, self)._structure_insert_row(_row_idx,_row_data) def _structure_update_row(self, _row_idx, _row_data, _commit=True, _no_logging=None): if _commit is True: """Override parent to add XML handling""" # Last column is a reference print("_row_data: " + str(_row_data)) _row_node = self.data_table[_row_idx][len(self.data_table[_row_idx]) -1] self._structure_populate_row(_row_node, _row_data) # Call parent super(XpathDataset, self)._structure_update_row(_row_idx,_row_data) def _structure_delete_row(self, _row_idx, _commit=True, _no_logging=None): if _commit is True: """Override parent to add XML handling""" _row_node = self.data_table[_row_idx][len(self.data_table[_row_idx]) -1] self._structure_row_node_parent.remove(_row_node) # Call parent super(XpathDataset, self)._structure_delete_row(_row_idx) #self.data_table.pop(_row_idx)
[docs] def save(self, _save_as = None): """Save the document""" if not _save_as: _save_as = make_path_absolute(self.filename, self._base_path()) self._structure_tree.write(_save_as) self.log_save(_save_as) return self._log