pretxt0 = ('oa', 'ob', 'oc', 'od', 'oe', 'of', 'og', 'oh', 'oi', 'oj', 'ok', 'ol', 'om', 'on', 'oo', 'op', 'oq', 'or', 'os', 'ot', 'ou', 'ov', 'ow', 'ox', 'oy', 'oz')
for pretxt in pretxt0:
    doc = open (pretxt + '.txt','w')
    aa = ["aa.cn", "ab.cn", "zv.cn", "zw.cn", "zx.cn", "zy.cn", "zz.cn"]
    with open('domain_cn_' + pretxt + '.txt','r') as foo:
        doo = foo.readlines()
        for ab in aa:
            a = 'Domain Name: ' + pretxt + ab + '\n'
            if a not in doo: 
                print (pretxt + ab,file = doc)
    doc.close()