循环浏览字典中嵌入的列表列表中的所有项目

Question

I have dates in string form in list of lists in a dictionary. I wrote a function to convert date strings to datetimes. I would like to convert all string dates in my dictionary to date times. My code only converts the first sublist in each table and it has no way of getting the others. What's the best way to do this?

import datetime

def parse_date(datestamp):
      try:
          return datetime.datetime.strptime(str(datestamp)[:10], '%Y-%m-%d')
      except ValueError:
          pass

My_Dict = {
    'Value1': {'Dates' : [['2014-10-14', 10, '2014-10-13', '2014-11-03'], ['2014-10-14', '2014-10-14', '2014-11-03']]},
    'Value2': {'Dates' : [['2014-10-14', '2014-10-13', '2014-11-03'], ['2014-10-14', '2014-10-14', '2014-11-03']]},
    }

for tbl in My_Dict:
    print [parse_date(x) for x in My_Dict[tbl]['Dates'][0]]

Answer 1

It's a matter of expanding out your nested lists correctly:

for key in My_Dict:
    for data in My_Dict[key]["Dates"]:
        for date in data:
            print date, parse_date(date)

Gives:

2014-10-14 2014-10-14 00:00:00
2014-10-13 2014-10-13 00:00:00
2014-11-03 2014-11-03 00:00:00
2014-10-14 2014-10-14 00:00:00
2014-10-14 2014-10-14 00:00:00
2014-11-03 2014-11-03 00:00:00
2014-10-14 2014-10-14 00:00:00
10 None
2014-10-13 2014-10-13 00:00:00
2014-11-03 2014-11-03 00:00:00
2014-10-14 2014-10-14 00:00:00
2014-10-14 2014-10-14 00:00:00
2014-11-03 2014-11-03 00:00:00

To put this into a single flat list you could do:

print [parse_date(date) for key in My_Dict for data in My_Dict[key]["Dates"] for date in data]

but I think the three loops are much easier to read!

Answer 2

Nest your list comprehension as

print [[parse_date(x) for x in i] for i in My_Dict[tbl]['Dates']]

But if you want a flat list, then you can try as Hooke mentioned, that is

print [parse_date(date) for key in My_Dict for data in My_Dict[key]["Dates"] for date in data]