Python Cookbook

Autodetecting XML Encoding

Credit: Paul Prescod

Problem

You have XML documents that may use a large variety of Unicode encodings, and you need to find out which encoding each document is using.

Solution

This is a task that we need to code ourselves, rather than getting an existing package to perform it, if we want complete generality:

import codecs, encodings """ Caller will hand this library a buffer and ask it to convert it or autodetect the type. """ # None represents a potentially variable byte. "##" in the XML spec... autodetect_dict={ # bytepattern : ("name", (0x00, 0x00, 0xFE, 0xFF) : ("ucs4_be"), (0xFF, 0xFE, 0x00, 0x00) : ("ucs4_le"), (0xFE, 0xFF, None, None) : ("utf_16_be"), (0xFF, 0xFE, None, None) : ("utf_16_le"), (0x00, 0x3C, 0x00, 0x3F) : ("utf_16_be"), (0x3C, 0x00, 0x3F, 0x00) : ("utf_16_le"), (0x3C, 0x3F, 0x78, 0x6D): ("utf_8"), (0x4C, 0x6F, 0xA7, 0x94): ("EBCDIC") } def autoDetectXMLEncoding(buffer): """ buffer -> encoding_name The buffer should be at least four bytes long. Returns None if encoding cannot be detected. Note that encoding_name might not have an installed decoder (e.g., EBCDIC) """ # A more efficient implementation would not decode the whole # buffer at once, but then we'd have to decode a character at # a time looking for the quote character, and that's a pain encoding = "utf_8" # According to the XML spec, this is the default # This code successively tries to refine the default: # Whenever it fails to refine, it falls back to # the last place encoding ...