分析一个程序

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程序来自http://wiki.woodpecker.org.cn/moin/MiscItems/2011-11-28

#!/usr/bin/pythonimport sysimport randomimport timeimport itertoolsimport operatorimport collections# 返回一个包含在指定范围内产生包含随机数的字典def g(length, typerange):    return [{'type':random.randint(0,typerange),'data':'hello%s' % x } for x in xrange(length)]def f1(qrs):   li=[]   qrs.sort(key=operator.itemgetter('type'))   for k,g in itertools.groupby(qrs,key=operator.itemgetter('type')):       li.append({'type':k,'data':[i['data'] for i in g]})   return lidef f2(qrs):    d = collections.defaultdict(list)    for q in qrs:       d[q['type']].append(q['data'])    result = [{'type': k, 'data': v} for k, v in d.items()]    return resultdef f3(qrs):    new_list = {}    for elem in qrs:        new_list.setdefault(elem['type'], []).append(elem['data'])    result = [{'type': k, 'data': v} for k, v in new_list.items()]    return resultdef t(f, a):    start = time.time()    f(a)    end = time.time()    return end - startdef main():    l = 100000  #范围的上限    tr = 10  #步长    try:       l = int(sys.argv[1])    except:       pass    try:       tr = int(sys.argv[2])    except:       pass    print 'groupby     %s' % t(f1,g(l,tr))    print 'defaultdict %s' % t(f2,g(l,tr))    print 'setdefault  %s' % t(f3,g(l,tr))if __name__ == '__main__':    main()

函数t()用来计算f()的运行时间。t()的参数f是要执行的函数。

用到的几个模块和函数