为什么打印错误的结果

Question

我是python的新手，今天我写了一个程序从一些数据集中获取最大值对，但是我写的程序没有给我正确的答案，代码是

#!/usr/bin/python

import sys

maxsale = 0
oldKey = None
# Loop around the data
# It will be in the format key\tval
# Where key is the store name, val is the sale amount
#
# All the sales for a particular store will be presented,
# then the key will change and we'll be dealing with the next store

for line in sys.stdin:
    data_mapped = line.strip().split("\t")
    if len(data_mapped) != 2:
        # Something has gone wrong. Skip this line.
        continue

    thisKey, thisSale = data_mapped

    if oldKey and oldKey != thisKey:
        print oldKey, "\t", maxsale
        oldKey = thisKey;
        oldsale = 0

    oldKey = thisKey
    if maxsale < thisSale:
        maxsale = thisSale
if oldKey != None:
    print oldKey, "\t", maxsale

数据集是：

Anchorage       298.86
Anchorage       6.38
Aurora  34.1
Aurora  10.6
Aurora  55.7
Austin  327.75
Austin  379.6
Austin  469.63
Austin  11.6

结果是：

Anchorage   6.38
Aurora  34.1
Austin  469.63

有人能帮我处理这个问题吗？提前谢谢！你知道吗

Answer 1

首先，您没有将输入转换为数字。这意味着任何以'6'开头的“数”都大于任何以'2'开头的“数”，即使是像'6.38'和'198.86'这样的值。你知道吗

thisKey, thisSale = data_mapped
thisSale = float(thisSale)

接下来，将oldSale设置为0，但从不引用它。我想你是想在那里做maxSale = 0，重置一个新商店的值。你知道吗

最后，您不需要在if块中使用oldKey = thisKey;，因为您会在之后立即这样做。你知道吗

请注意，当您将值转换为该货币的最小面额并使用整数时，货币计算效果最佳，因为浮点计算并不总是完全准确的，而且可能会出现舍入错误。看起来您的数据不能保证有尾随的零，因此您必须检查字符串中是否有小数点，如果存在小数点，则在小数点上拆分，等等。你知道吗

thisKey, thisSale = data_mapped
if '.' not in thisSale:
    thisSale = int(thisSale)*100
else:
    dollars, cents = thisSale.split('.')
    if len(cents) < 2:
        cents += '0'
    thisSale = int(dollars)*100 + int(cents)

对表示美分数的整数执行财务计算，然后根据显示需要将值格式化为美元和美分：

>>> '%.2f' % (29886/100.)
'298.86'
>>> '{:.02f}'.format(29886/100.)
'298.86'

Answer 2

#!/usr/bin/python

import sys

maxsale = 0
oldKey = None
# Loop around the data
# It will be in the format key\tval
# Where key is the store name, val is the sale amount
#
# All the sales for a particular store will be presented,
# then the key will change and we'll be dealing with the next store
d = dict() 
for line in sys.stdin:
    data_mapped = line.strip().split("\t")
    if len(data_mapped) != 2:
        # Something has gone wrong. Skip this line.
        continue

    key,value = data_mapped
    if (key in d) and d[key] < float(value):
        d[key] = float(value)
    elif not key in d:
        d[key] = float(value)

for k,v in d.items():
    print k,'\t',v