从列表中提取元素？

Question

我不认为我的return语句通过了所有的测试用例（带有空字符串的测试用例）。@FLOTUS不是一个提词，因为提词应该以空格开头，或者更确切地说是tweet的开始。因此它应该作为空字符串传递。任何帮助，将不胜感激如何解决这个问题！你知道吗

def extract_mentions(tweet):
    ''' (str) -> list of str

Return a list containing all of the mentions in the tweet, in the order, they appear in the tweet.
Note: This definition of a mention doesn't allow for mentions embedded in other symbols.

Note: This definition of a mention doesn't allow for mentions embedded in other symbols.

>>> extract_mentions('@AndreaTantaros - You are a true journalistic professional. I so agree with what you say. Keep up the great work! #MakeAmericaGreatAgain')
['AndreaTantaros']
>>> extract_mentions('I'm joining @PhillyD tonight at 7:30 pm PDT / 10:30 pm EDT to provide commentary on tonight's #debate. Watch it here.')
['PhillyD']
>>> extract_mentions('Join me live in @Springfield, @ohio!')
['Springfield, ohio']
>>> extract_mentions('They endured beatings and jail time. They sacrificed their lives for this right@FLOTUS')
[''] '''

return [tag.strip('@') for tag in tweet.split() if tag.startswith('@')]

Answer 1

就我个人而言，我会使用Wiktor在评论中提出的一个很好的正则表达式，但是如果您想避免它，请尝试[tag[tag.index('@')+1:] for tag in tweet.split() if '@' in tag]

它所做的是，如果在拆分的令牌中发现一个“@”字符，它将从@的下一个字母开始返回令牌。例如，如果tag='b@a123，那么它将返回tag[2:]，即a123。你知道吗