Question

我是python中的新人，今天我编写了一个程序来从一些数据集中获取最大值对，但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

任何人都可以帮我处理这个问题吗？提前谢谢你！

Answer 1

首先，您不是将输入转换为数字。这意味着任何＆＃34;数字＆＃34;以'6'开头的数字大于任何＆＃34;数字＆＃34;以'2'开头，即使是'6.38'和'198.86'等值。

thisKey, thisSale = data_mapped
thisSale = float(thisSale)

接下来，您将oldSale设置为0，但从不参考它。我认为你打算在那里做maxSale = 0，重置新商店的价值。

最后，您在oldKey = thisKey;区块中不需要if，因为您之后会立即执行此操作。

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，因为浮点计算并非始终完全准确，您可能会出现舍入错误。看起来您的数据不能保证有尾随零，因此您必须检查字符串中的小数点，如果存在，则分成小数点，依此类推。

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)

对表示分数的整数进行财务计算，然后在必要时将值格式化为美元和分数以用于显示目的：

>>> '%.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

为什么打印错误的结果？

2 个答案: