python 在Unicode和普通字符串 str 之间转换

unicodestring = u"Hello world"
# 将Unicode转化为普通Python字符串："encode"
utf8string = unicodestring.encode("utf-8")
asciistring = unicodestring.encode("ascii")
isostring = unicodestring.encode("ISO-8859-1")
utf16string = unicodestring.encode("utf-16")
# 将普通Python字符串转化为Unicode："decode"
plainstring1 = unicode(utf8string, "utf-8")
plainstring2 = unicode(asciistring, "ascii")
plainstring3 = unicode(isostring, "ISO-8859-1")
plainstring4 = unicode(utf16string, "utf-16")
assert plainstring1 == plainstring2 == plainstring3 == plainstring4 

def unicode2str(p_unicode):
    v = p_unicode.encode('unicode-escape').decode('string_escape') if p_unicode is not None else None
    return v

def str2unicode(p_str):
    v = p_str.decode('unicode-escape') if p_str is not None else None
    return v