str和unicode

ustring = u"unicode string"
print ustring, type(ustring)    #unicode string 
normalstring = "normal string"
print normalstring, type(normalstring) #normal string 
print type(ustring).__bases__  #(,)
print type(normalstring).__bases__  #(,)

判断一个变量是否为字符串，普通字符串，Unicode字符串

isinstance(a, basestring)
isinstance(a, str)
isinstance(a, unicode)