import re


def word_filter(word):
    """ The filter used for deleting the noisy words in changed code.
    Here is the method:
        1. Delete character except for digit, alphabet, '_'.
        2. the word shouldn't be all digit.
        3. the length should large than 2.
    Args:
        word
    Returns:
        True for not filtering, False for filtering.
    """
    if word[:2] == '0x':
        return False
    if '=' in word:
        return False
    if '/' in word:
        return False
    if '.' in word:
        return False
    if '$' in word:
        return False
    word = re.sub("[^0-9A-Za-z_]", "", word)
    if(word.isdigit()):
        return False
    if(len(word) <= 2):
        return False
    return True