字典python上的零除错误

Question

def getSortedKeyList(dl):
    kl = list(dl.items())
    kl.sort()
    return kl

def tupleListToDict(a):
    b = {}
    for k, v in a:
        b[k] = b.get(k, [])+v
    return b

def main():
    gradeList = [('Zaphod', [33, 20]), ('Zaphod', [75, 48]), \
                 ('Slartibartfast', []), ('Trillian', [98, 88]), \
                 ('Trillian', [97, 77]), ('Slartibartfast', []), \
                 ('Marvin', [2000, 500]), ('Authur', [42, 20]), \
                 ('Authur', [64]), ('Trillian', [99]), \
                 ('Marvin', [450]), ('Marvin', [550]), \
                 ('Agrajag', []), ('Agrajag', []), ('Agrajag', [0]), \
                 ('Ford', [50]), ('Ford', [50]), ('Ford', [50])]

    print('\t', '\t', "Grade", '\t')
    print('\t', "Name", '\t', "Count", '\t', "Average")
    print("-----------------------------------------")

    dicList = tupleListToDict(gradeList)            
    dicList = getSortedKeyList(dicList)

    for k, v in dicList:
        print(k, len(v), '\t', sum(v)/len(v))

我正试着用字典做一张桌子。首先，我将元组转换为dictionary，并按键对dictionary进行排序。接下来，我将尝试打印出（keys，num of keys，average）。然而，当我尝试对平均部分做sum（v）/len（v）时，我得到的除法是零误差。为了避免这个错误，我尝试将字典中的空值返回到0，但是我不知道怎么做。请帮忙。你知道吗

Answer 1

def getSortedKeyList(dl):
    kl = list(dl.items())
    kl.sort()
    return kl

def tupleListToDict(a):
    b = {}
    for k, v in a:
        b[k] = b.get(k, [])+v
    return b

def main():
    gradeList = [('Zaphod', [33, 20]), ('Zaphod', [75, 48]), \
                 ('Slartibartfast', []), ('Trillian', [98, 88]), \
                 ('Trillian', [97, 77]), ('Slartibartfast', []), \
                 ('Marvin', [2000, 500]), ('Authur', [42, 20]), \
                 ('Authur', [64]), ('Trillian', [99]), \
                 ('Marvin', [450]), ('Marvin', [550]), \
                 ('Agrajag', []), ('Agrajag', []), ('Agrajag', [0]), \
                 ('Ford', [50]), ('Ford', [50]), ('Ford', [50])]

    print('\t', '\t', "Grade", '\t')
    print('\t', "Name", '\t', "Count", '\t', "Average")
    print("                    -")

    dicList = tupleListToDict(gradeList)            
    dicList = getSortedKeyList(dicList)

    for k, v in dicList:
      try:
          print(k, len(v), '\t', sum(v)/len(v))
     except ZeroDivisionError as detail:
          print('Handling run-time error:', detail)

通过try-and-catch块可以捕获异常错误

Answer 2

Slartibartfast没有分数，因此当你看到他的记录时，len(v)是0。你知道吗

根据他的“平均值”应该是多少，您可以将最后一个循环修改为：

for k, v in dicList:
    print(k, len(v), '\t', sum(v)/len(v) if len(v)>0 else 'N/A')