Python:查找每个月的平均股票值(value)

Question

基本上我有一个包含数据和价格的元组列表，例如:

[ ("2013-02-12", 200.0), ("2012-02-25", 300.0), ("2000-03-04", 100.0), ("2000-03-05", 50.0)]

该函数需要找到每个月的平均股票值(value)，然后返回包含日期(月份和年份)和股票价格的元组列表。像这样的东西:

[(250.0, "02-2013"), (100.0, "03-2000"), (50.0, "03-2000")]

这是我目前的代码:

def average_data(list_of_tuples = []):

    list_of_averages = []
    current_year_int = 2013
    current_month_int = 2
    sum_float = float()
    count = 0
    for dd_tuple in list_of_tuples:
        date_str = dd_tuple[0]
        data_float = dd_tuple[1]
        date_list = date_str.split("-")
        year_int = int(date_list[0])
        month_int = int(date_list[1])
        date_year_str = "Date: " + str(month_int) + "-" + str(year_int);


        if month_int != current_month_int:
            average_float = sum_float / count
            average_list = [date_year_str, average_float]
            average_tuple = tuple(average_list)
            list_of_averages.append(average_tuple)
            current_month_int = month_int
            sum_float += data_float


        sum_float += data_float
        count += 1
        current_month_int = month_int
        current_year_int = year_int


    return list_of_averages

它返回一个平均值，但不是正确的，也许不是全部？我曾尝试查看互联网上的示例并询问我的助教(这是针对 python 类的)但无济于事。有人能指出我正确的方向吗？

编辑:根据建议，if 语句现在应该如下所示，对吗？

    if month_int != current_month_int:
        average_float = sum_float / count
        average_list = [date_year_str, average_float]
        average_tuple = tuple(average_list)
        list_of_averages.append(average_tuple)
        current_month_int = month_int
        sum_float = 0.0
        count = 0
        sum_float += data_float
        count += 1

编辑:感谢大家的帮助!我现在已经运行了代码。

Answer 1

>>> lis = [ ("2013-02-12", 200.0), ("2012-02-25", 300.0), ("2000-03-04", 100.0), ("2000-03-05", 50.0)]
>>> from collections import defaultdict
>>> dic = defaultdict(list)
>>> for k,val in lis:
        key = "-".join(k.split('-')[:-1][::-1])             
        dic[key].append(val)
...     
>>> [(sum(v)/float(len(v)),k)  for k,v in dic.items()]

[(200.0, '02-2013'), (300.0, '02-2012'), (75.0, '03-2000')]

上述代码的简化版本:

lis = [ ("2013-02-12", 200.0), ("2012-02-25", 300.0), ("2000-03-04", 100.0), ("2000-03-05", 50.0)]
dic = {}
for date, val in lis:
    #split the date string at '-' and assign the first  2 items to  year,month
    year, month = date.split('-')[:2]
    #now check if (month,year) is there in the dict
    if (month, year) not in dic:
        #if the tuple was not found then initialise one with an empty list
        dic[month,year] = []

    dic[month,year].append(val) # append val to the (month,year) key

print dic
#Now iterate over key,value items and do some calculations to get the desired output
sol =[]
for key, val in dic.items():
    new_key = "-".join(key)
    avg = sum(val) / len(val)
    sol.append((avg, new_key))
print sol

输出:

#print dic
{('03', '2000'): [100.0, 50.0],
 ('02', '2013'): [200.0],
 ('02', '2012'): [300.0]}
#print sol
[(75.0, '03-2000'), (200.0, '02-2013'), (300.0, '02-2012')]