utils.py

def sanitize_log_data(secret, data=None, leave_characters=4):
    """
    Clean private/secret data from log statements and other data.

    Assumes data and secret are strings. Replaces all but the first
    `leave_characters` of `secret`, as found in `data`, with '*'.

    If no data is given, all but the first `leave_characters` of secret
    are simply replaced and returned.
    """
    replace_secret = (secret[:leave_characters] +
                      (len(secret) - leave_characters) * '*')

    if data:
        return data.replace(secret, replace_secret)

    return replace_secret