[Tutor] creating dictionary from a list

[Mark Lawrence]

On 13/04/2013 15:34, Saad Bin Javed wrote:
> I ran into a bit of problem with my revised code based on Steven's
> suggestions.
>
> lst = ['', 'Thu Apr 04           Weigh In', '', 'Sat Apr 06 Collect
> NIC', '                     Finish PTI Video', '', 'Wed Apr 10  Serum
> uric acid test', '', 'Sat Apr 13   1:00pm  Get flag from dhariwal', '',
> 'Sun Apr 14      Louis CK Oh My God', '', '']
>
> lst = filter(None, lst)
> lst = [item.split('  ') for item in lst]
> lst = [item for sublist in lst for item in sublist]
> lst = filter(None, lst)
>
> This code would produce:
>
> ['Thu Apr 04', ' Weigh In', 'Sat Apr 06', ' Collect NIC', ' Finish PTI
> Video', 'Wed Apr 10', ' Serum uric acid test', 'Sat Apr 13', ' 1:00pm',
> 'Get flag from dhariwal', 'Sun Apr 14', ' Download Louis CK Oh My God']
>
> dict = {}
> for item in lst:
>      if item.startswith(('Mon','Tue','Wed','Thu','Fri','Sat','Sun')):
>
>          dict.update({lst[lst.index(item)].lstrip():
> lst[lst.index(item)+1].lstrip()})
> print dict
>
> Such a dictionary would only add the item next to the date as the value.
> But from the list you can see 'Sat Apr 06' has two items on the agenda
> while 'Sat Apr 13' show item and a time. So you can understand why such
> a dict would be useless.
>
> I want all agenda items joined as a comma delimited string and added to
> the date key as a value. I've been mulling over how to go about it. One
> idea was to get indices of dates in the list and add all items in
> between them as values.
>
> index_keys = [] #0, 2, 5, 7, 9
> index_values = [] #1, 3, 4, 6, 8, 10
> for item in lst:
>      if
> item.lstrip().startswith(('Mon','Tue','Wed','Thu','Fri','Sat','Sun')):
>          index_keys.append(lst.index(item))
>      else:
>          index_values.append(lst.index(item))
>
> But I can't quite get it to understand that i want all items between
> position 0 and 2 in the list to be assigned to item at 0 in the
> dictionary and so forth.
>
> Ideas?
>

Don't fight Python, unlike this chap[1] :)  Basically if you're looping 
around any data structure you rarely need to use indexing, so try this 
approach.

for item in lst:
     if item.startswith(('Mon','Tue','Wed','Thu','Fri','Sat','Sun')):
         myDict[item] = []
         saveItem = item
     else:
         myDict[saveItem].append(item.strip())


[1]http://www.bbc.co.uk/news/world-us-canada-22118773

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Mark Lawrence