Python实现简单HTML表格解析的方法

#The goal of table parser is to get specific information from specific
#columns in a table.
#Input: source code from a typical website
#Arguments: a list of headers the user wants to return
#Output: A list of lists of the data in each row
import libxml2dom
def parse_tables(source, headers, table_index):
  """parse_tables(string source, list headers, table_index)
    headers may be a list of strings if the table has headers defined or
    headers may be a list of ints if no headers defined this will get data
    from the rows index.
    This method returns a list of lists
    """
  #Determine if the headers list is strings or ints and make sure they
  #are all the same type
  j = 0
  print 'Printing headers: ',headers
  #route to the correct function
  #if the header type is int
  if type(headers[0]) == type(1):
    #run no_header function
    return no_header(source, headers, table_index)
  #if the header type is string
  elif type(headers[0]) == type('a'):
    #run the header_given function
    return header_given(source, headers, table_index)
  else:
    #return none if the headers aren't correct
    return None
#This function takes in the source code of the whole page a string list of
#headers and the index number of the table on the page. It returns a list of
#lists with the scraped information
def header_given(source, headers, table_index):
  #initiate a list to hole the return list
  return_list = []
  #initiate a list to hold the index numbers of the data in the rows
  header_index = []
  #get a document object out of the source code
  doc = libxml2dom.parseString(source,html=1)
  #get the tables from the document
  tables = doc.getElementsByTagName('table')
  try:
    #try to get focue on the desired table
    main_table = tables[table_index]
  except:
    #if the table doesn't exits then return an error
    return ['The table index was not found']
  #get a list of headers in the table
  table_headers = main_table.getElementsByTagName('th')
  #need a sentry value for the header loop
  loop_sentry = 0
  #loop through each header looking for matches
  for header in table_headers:
    #if the header is in the desired headers list 
    if header.textContent in headers:
      #add it to the header_index
      header_index.append(loop_sentry)
    #add one to the loop_sentry
    loop_sentry+=1
  #get the rows from the table
  rows = main_table.getElementsByTagName('tr')
  #sentry value detecting if the first row is being viewed
  row_sentry = 0
  #loop through the rows in the table, skipping the first row
  for row in rows:
    #if row_sentry is 0 this is our first row
    if row_sentry == 0:
      #make the row_sentry not 0
      row_sentry = 1337
      continue
    #get all cells from the current row
    cells = row.getElementsByTagName('td')
    #initiate a list to append into the return_list
    cell_list = []
    #iterate through all of the header index's
    for i in header_index:
      #append the cells text content to the cell_list
      cell_list.append(cells[i].textContent)
    #append the cell_list to the return_list
    return_list.append(cell_list)
  #return the return_list
  return return_list
#This function takes in the source code of the whole page an int list of
#headers indicating the index number of the needed item and the index number
#of the table on the page. It returns a list of lists with the scraped info
def no_header(source, headers, table_index):
  #initiate a list to hold the return list
  return_list = []
  #get a document object out of the source code
  doc = libxml2dom.parseString(source, html=1)
  #get the tables from document
  tables = doc.getElementsByTagName('table')
  try:
    #Try to get focus on the desired table
    main_table = tables[table_index]
  except:
    #if the table doesn't exits then return an error
    return ['The table index was not found']
  #get all of the rows out of the main_table
  rows = main_table.getElementsByTagName('tr')
  #loop through each row
  for row in rows:
    #get all cells from the current row
    cells = row.getElementsByTagName('td')
    #initiate a list to append into the return_list
    cell_list = []
    #loop through the list of desired headers
    for i in headers:
      try:
        #try to add text from the cell into the cell_list
        cell_list.append(cells[i].textContent)
      except:
        #if there is an error usually an index error just continue
        continue
    #append the data scraped into the return_list    
    return_list.append(cell_list)
  #return the return list
  return return_list