python string.py 源碼分析 二：capwords

def capwords(s, sep=None):
    """capwords(s [,sep]) -> string

    Split the argument into words using split, capitalize each
    word using capitalize, and join the capitalized words using
    join.  If the optional second argument sep is absent or None,
    runs of whitespace characters are replaced by a single space
    and leading and trailing whitespace are removed, otherwise
    sep is used to split and join the words.

    """
    return (sep or ' ').join(x.capitalize() for x in s.split(sep))

本語句很是精秒

先看join這個內置方法

",".join(["2","3","4"]) 結果爲"2,3,4" 

capitalize() 首字母大寫

split(sep)以sep爲目標分割字符串

以正常思惟寫法是

def capwords(s, sep=None):
    lt = []
    for x in s.split(sep):
        lt.append(x.capitalize())
    return (sep or ' ').join(lt)

 

能以一句這麼精簡的語句實現，真是太牛了。