Encoding detecting Python open() - Automatically detects encoding of existing text files for reading and writing

chardet_open.py

from chardet.universaldetector import UniversalDetector # pip install chardet
import io
import os.path

def open(file, mode='r', buffering=-1, encoding=None, errors=None,
                 newline=None, closefd=True):
    """ A wrapper for io.open(), which tries to detect the encoding of a file
    using chardet before reading or writing 
    
    Supports all arguments of io.open(). "encoding" is only used if file does
    not exist.
    
    Binary mode is not supported.
    
    Usage:
    
    >>> import chardet_open
    >>> my_fh = chardet_open.open('french-iso.txt', mode="r+")
    >>> print my_fh.encoding
    ISO-8859-1
    >>> print my_fh.read()
    Wikipédia est un projet dencyclopédie...

    """
       
    if 'b' in mode:      
        raise Exception("binary mode not supported")
     
    
    if os.path.exists(file):
        raw_file = io.open(file, mode='rb')
        
        detector = UniversalDetector()
        for line in raw_file.readlines():
            detector.feed(line)
            if detector.done: break
        detector.close()
        
        raw_file.close()
        
        encoding = detector.result["encoding"]    
      
    decoding_fh = io.open(file, mode=mode, buffering=buffering,
                          encoding=encoding, 
                          errors=errors,
                          newline=newline,
                          closefd=closefd)

    return decoding_fh