思路: 用 re 的匹配

## First Word
# 
import re
def first_word(text: str) -> str:
    """
        returns the first word in a given text.
    """
    # your code here
 
    pat1 = "[a-zA-Z']+"
    result = re.search(pat1,text)
    result = str(result.group())
    return result
if __name__ == '__main__':
    print("Example:")
    print(first_word("Hello world"))
    
    # These "asserts" are used for self-checking and not for an auto-testing
    assert first_word("Hello world") == "Hello"
    assert first_word(" a word ") == "a"
    assert first_word("don't touch it") == "don't"
    assert first_word("greetings, friends") == "greetings"
    assert first_word("... and so on ...") == "and"
    assert first_word("hi") == "hi"
    assert first_word("Hello.World") == "Hello"
    print("Coding complete? Click 'Check' to earn cool rewards!")

体会:

1. [a-zA-Z']+ 匹配多个字母与'
2. re.search(pat1,text) 返回匹配的第一个, 类似这种<_sre.SRE_Match object; span=(0, 4), match='asda'> 对象
3. group 函数 返回匹配的字符串