Python2.X如何將Unicode中文字符串轉換成 string字符串

普通字符串能夠用多種方式編碼成Unicode字符串，具體要看你究竟選擇了哪一種編碼：
unicodestring = u"Hello world"
# 將Unicode轉化爲普通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") 
# 將普通Python字符串轉化爲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