Python组和总和

Question

我有一个元组列表:

Listoftuples=[
    (0.021892733407683305, 0.14887058717224647, 4.573173081530965, 0.04619366749021177, u'0102'),
    (0.08416364174734663, 0.8500527816482009, 23.649983331004403, 0.0, u'0103'),
    (0.02181070623592521, 0.15049387302788395, 1.2098398749067714, 1.6037412295275804, u'0102')
    ]

我想每组(group =元组中的最后一个值,例如u'0102'):

• 总结第一个价值
• 汇总第二个值并除以第一个值的总和

尝试:

import itertools

Listoftuples=[
    (0.021892733407683305, 0.14887058717224647, 4.573173081530965, 0.04619366749021177, u'0102'),
    (0.08416364174734663, 0.8500527816482009, 23.649983331004403, 0.0, u'0103'),
    (0.02181070623592521, 0.15049387302788395, 1.2098398749067714, 1.6037412295275804, u'0102')
    ]

keyfunc=lambda t: (t[4])
Listoftuples.sort(key=keyfunc)

for key,rows in itertools.groupby(Listoftuples, keyfunc):
    sumOfFirstValue = sum(r[0] for r in rows)
    sumOfSecondDividedBySumOfFirst= sum(r[1] for r in rows)/sumOfFirstValue
    print key,sumOfFirstValue,sumOfSecondDividedBySumOfFirst

结果:

0102 0.0437034396436 0.0
0103 0.0841636417473 0.0

最后的零值.我该如何解决？

Answer 1

一个常见的错误是认为rows返回来自groupby具体列表.实际上它是一个迭代器,在计算时已经筋疲力尽了sumOfFirstValue.解决方法是:

...
for key,rows in itertools.groupby(Listoftuples, keyfunc):
    rows = list(rows)
    ...