html-parser-example.py

#!/usr/bin/python
import re

class HtmlElement:
    def __init__(self, tag, attributes={}, children=[], parent=None):
        if type(tag) != str: raise TypeError("\"tag\" must be a string.")
        if type(attributes) != dict: raise TypeError("\"attributes\" must be a dictionary.")
        if type(children) != list: raise TypeError("\"children\" must be a list.")
        if type(parent) != HtmlElement and parent != None: raise TypeError("\"parent\" must be a HtmlElement or None.")
        self._tag = tag
        self._attributes = attributes
        self._children = children
        self._parent = parent
    def get_parent(self):
        return self._parent
    def get_children(self):
        return self._children
    def get_tag(self):
        return self._tag
    def get_attributes(self):
        return self._attributes
    def get_attribute(self, name):
        for attribute in self._attributes:
            if attribute.lower() == name.lower(): return self._attributes[attribute]
        return False
    def set_attribute(self, name, value):
        for attribute in self._attributes:
            if attribute.lower() == name.lower():
                self._attributes[attribute] = value
                return
        self._attributes[name] = value
    def append_child(self, child):
        if type(child) not in (str, HtmlElement):
            raise TypeError("\"child\" must be either a string or HtmlElement.")
        self._children.append(child)
    def get_element_by_id(self, id):
        for child in self._children:
            if type(child) != HtmlElement: continue
            for attribute in child._attributes:
                if attribute.lower() == "id" and child._attributes[attribute] == id: return child
            element = child.get_element_by_id(id)
            if element: return element
        return None
    def get_elements_by_name(self, name):
        elements = []
        for child in self._children:
            if type(child) != HtmlElement: continue
            for attribute in child._attributes:
                if attribute.lower() == "name" and child._attributes[attribute].lower() == name.lower(): elements.append(child)
            elements += child.get_elements_by_name(name)
        return elements
    def get_elements_by_class_name(self, class_name):
        elements = []
        for child in self._children:
            if type(child) != HtmlElement: continue
            for attribute in child._attributes:
                if attribute.lower() == "class" and class_name.lower() in [name.lower() for name in re.split("[ \t]+", child._attributes[attribute])]: elements.append(child)
            elements += child.get_elements_by_class_name(class_name)
        return elements
    def get_elements_by_tag_name(self, tag_name):
        elements = []
        for child in self._children:
            if type(child) != HtmlElement: continue
            if child._tag.lower() == tag_name.lower(): elements.append(child)
            elements += child.get_elements_by_tag_name(tag_name)
        return elements
    def __iter__(self):
        for child in self._children:
            yield child
    def __str__(self):
        if self._tag != "":
            html = "<%s"%self._tag
            if len(self._attributes) > 0:
                html += " " + " ".join(["%s=\"%s\""%(name, self._attributes[name]) if self._attributes[name] else name for name in self._attributes])
            if len(self._children) == 0:
                if self._tag[0] != "!":
                    return html + "/>"
                else:
                    return html + ">"
            html += ">"
        else:
            html = ""
        for child in self._children:
            html += str(child)
        if self._tag != "":
            return html + "</%s>"%self._tag
        else:
            return html

def parse_html(html, close_implicit=["meta","br","img","link"]):
    if type(html) != str: raise TypeError("\"html\" must be a string.")
    if type(close_implicit) not in (list, tuple): raise TypeError("\"close_implicit\" must be a list or tuple.")
    close_implicit = [tag.lower() for tag in close_implicit]
    root = HtmlElement("")
    tags = []
    in_tag = False
    tag = ""
    text = ""
    current = root
    for c in html:
        if c == "<" and not in_tag:
            if len(text) > 0:
                current.append_child(text)
                text = ""
            in_tag = True
        elif c == ">" and in_tag:
            in_tag = False
            if len(tag) == 0: pass
            elif len(tag) >= 3 and (tag[:3] == "!--" and tag[-2::] == "--"):
                pass
            elif tag[0] == "/":
                tag = tag[1:]
                if tags[-1].lower() == tag.lower():
                    current = current.get_parent()
                    tags.pop()
                else:
                    raise ValueError("invalid closing tag \"%s\" for \"%s\""%(tag, tags[-1]))
            elif tag[-1] == "/" or tag[0] == "!":
                tag = re.split("[ \t]+", tag.rstrip("/ "))
                attributes = {}
                for attribute in tag[1:]:
                    attribute = re.findall("([^=]+)(?:|=[\"]{0,1}[^\"]+[\"]{0,1})", attribute)
                    if len(attribute) <= 0: continue
                    if len(attribute) == 1:
                        attributes[attribute[0]] = None
                    else:
                        attributes[attribute[0]] = attribute[1].strip("\"")
                current.append_child(HtmlElement(tag[0],attributes,[],current))
            else:
                tag = re.split("[ \t]+", tag)
                attributes = {}
                for attribute in tag[1:]:
                    attribute = re.findall("([^=]+)(?:|=[\"]{0,1}[^\"]+[\"]{0,1})", attribute)
                    if len(attribute) <= 0: continue
                    if len(attribute) == 1:
                        attribute = attribute[0], None
                    else:
                        attribute = attribute[0], attribute[1].strip("\"")
                    attributes[attribute[0]] = attribute[1]
                if tag[0] in close_implicit:
                    current.append_child(HtmlElement(tag[0],attributes,[],current))
                else:
                    new = HtmlElement(tag[0],attributes,[],current)
                    current.append_child(new)
                    current = new
                    tags.append(tag[0])
            tag = ""
        elif in_tag:
            tag += c
        else:
            text += c
    if len(tags) > 0:
        raise ValueError("missing close tag for \"%s\""%tags[-1])
    if len(text) > 0:
        current.append_child(text)
    return root