Python3重放负向不工作

Question

我想检查在[a-zA-Z]之前没有attachment的字符串。

def is_attachment_url(url):
    """check url"""
    pattern = '(?<![\w]+)attachment'
    return re.search(pattern, url, re.I)


tests = (
    'article_?attachment',  # should be false
    'article_fattachment',  # should be false
    'article_-attachment',  # should be true
    'article_/attachment',  # should be true
)
for ss in tests:
    print(is_attachment_url(ss))

错误提示：

    raise error("look-behind requires fixed-width pattern")
sre_constants.error: look-behind requires fixed-width pattern

Answer 1

模式中的+使其变宽.您不需要它，因为您只想在“附件”之前检查单个字符，所以只需删除它：

pattern = '(?<![\w])attachment'