ValueError: max() arg is an

python 运行出错 ValueError: max() arg is an empty sequence

问题相关代码，请勿粘贴截图

def write_prf(i, mode):
    prf=get_prf(i,mode)
    max_prf_ = list(map(max，prf))
    average_prf_ =list(map(np.mean，prf))
    max_prf=list(map(str, max_prf_))
    average_prf=list(map(str, average_prf_))
    if  mode  ==  'u':

运行结果及报错内容

ValueError Traceback (most recent call last)
~\Desktop\ml-100k\main25.py in
372 recommend(args.itemcf,'item')
373 if name =='main':
--> 374 main()
375
376

~\Desktop\ml-100k\main25.py in main()
365 test(args.model)
366 else:
--> 367 test('usercf')
368 test('itemcf')
369 if args.usercf:

~\Desktop\ml-100k\main25.py in test(model)
271 prfs=[]
272 for i in range(1,6):
--> 273 prfs.append(write_prf(i,'u'))
274 cross_valid(prfs,'u')
275 #测试itemcf模型

~\Desktop\ml-100k\main25.py in write_prf(i, mode)
218 def write_prf(i, mode):
219 prf=get_prf(i,mode)
--> 220 max_prf_ = list(map(max, prf))
221 average_prf_ =list(map(np.mean, prf))
222 max_prf=list(map(str, max_prf_))

ValueError: max() arg is an empty sequence