def logrotate(filename):
    
    """
    Return the next available filename for a particular filename prefix.
    
    For example:
    
        >>> import os
        # Make three (empty) files in a directory
        >>> fp0 = open('file.0', 'w')
        >>> fp1 = open('file.1', 'w')
        >>> fp2 = open('file.2', 'w')
        >>> fp0.close(), fp1.close(), fp2.close()
        (None, None, None)
        # Use logrotate to get the next available filename.
        >>> logrotate('file')
        'file.3'
        >>> logrotate('file.2')
        'file.3'
        >>> logrotate('file.1')
        'file.3'
    
    This can be used to get the next available filename for logging, allowing
    you to rotate log files, without using Python's ``logging`` module.
    """

    match = re.match(r'(.*)' + re.escape(os.path.extsep) + r'(\d+)', filename)
    if os.path.exists(filename):
        if match:
            prefix, number = match.groups()
            number = int(number)
            while os.path.exists(os.path.extsep.join((prefix, str(number)))):
                number += 1
            return os.path.extsep.join((prefix, str(number)))
    elif match:
        return filename
    return logrotate(os.path.extsep.join((filename, '0')))
def logrotate(filename):
    
    """
    Return the next available filename for a particular filename prefix.
    
    For example:
    
        >>> import os
        # Make three (empty) files in a directory
        >>> fp0 = open('file.0', 'w')
        >>> fp1 = open('file.1', 'w')
        >>> fp2 = open('file.2', 'w')
        >>> fp0.close(), fp1.close(), fp2.close()
        (None, None, None)
        # Use logrotate to get the next available filename.
        >>> logrotate('file')
        'file.3'
        >>> logrotate('file.2')
        'file.3'
        >>> logrotate('file.1')
        'file.3'
    
    This can be used to get the next available filename for logging, allowing
    you to rotate log files, without using Python's ``logging`` module.
    """

    match = re.match(r'(.*)' + re.escape(os.path.extsep) + r'(\d+)', filename)
    if os.path.exists(filename):
        if match:
            prefix, number = match.groups()
            number = int(number)
            while os.path.exists(os.path.extsep.join((prefix, str(number)))):
                number += 1
            return os.path.extsep.join((prefix, str(number)))
    elif match:
        return filename
    return logrotate(os.path.extsep.join((filename, '0')))
def logrotate ( filename ) : match = re . match ( r'(.*)' + re . escape ( os . path . extsep ) + r'(\d+)' , filename ) if os . path . exists ( filename ) : if match : prefix , number = match . groups ( ) number = int ( number ) while os . path . exists ( os . path . extsep . join ( ( prefix , str ( number ) ) ) ) : number += 1 return os . path . extsep . join ( ( prefix , str ( number ) ) ) elif match : return filename return logrotate ( os . path . extsep . join ( ( filename , '0' ) ) )
Return the next available filename for a particular filename prefix.
    
    For example:
    
        >>> import os
        # Make three (empty) files in a directory
        >>> fp0 = open('file.0', 'w')
        >>> fp1 = open('file.1', 'w')
        >>> fp2 = open('file.2', 'w')
        >>> fp0.close(), fp1.close(), fp2.close()
        (None, None, None)
        # Use logrotate to get the next available filename.
        >>> logrotate('file')
        'file.3'
        >>> logrotate('file.2')
        'file.3'
        >>> logrotate('file.1')
        'file.3'
    
    This can be used to get the next available filename for logging, allowing
    you to rotate log files, without using Python's ``logging`` module.
Return the next available filename for a particular filename prefix . For example : >>> import os # Make three ( empty ) files in a directory >>> fp0 = open ( file . 0 w ) >>> fp1 = open ( file . 1 w ) >>> fp2 = open ( file . 2 w ) >>> fp0 . close () fp1 . close () fp2 . close () ( None None None ) # Use logrotate to get the next available filename . >>> logrotate ( file ) file . 3 >>> logrotate ( file . 2 ) file . 3 >>> logrotate ( file . 1 ) file . 3 This can be used to get the next available filename for logging allowing you to rotate log files without using Python s logging module .