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I've been whacking away at this for a while to no avail... Any help would be greatly appreciated.
I have:
[{'event': 0, 'voltage': 1, 'time': 0}, {'event': 0, 'voltage': 2, 'time': 1}, {'event': 1, 'voltage': 1, 'time': 2}, {'event': 1, 'voltage': 2, 'time': 3}, {'event': 2, 'voltage': 1, 'time': 4}, {'event': 2, 'voltage': 2, 'time': 5}, ...] and I want to split that list of dictionaries up per event like this (there can be arbitrarily many events):
list0 = [{'event': 0, 'voltage': 1, 'time': 0}, {'event': 0, 'voltage': 2, 'time': 1}] list1 = [{'event': 1, 'voltage': 1, 'time': 2}, {'event': 1, 'voltage': 2, 'time': 3}] list2 = [{'event': 2, 'voltage': 1, 'time': 4}, {'event': 2, 'voltage': 2, 'time': 5}] listN = ... 
701
To split the elements of a list in Python: Use a list comprehension to iterate over the list. On each iteration, call the split() method to split each string. Return the part of each string you want to keep.
To delete an item stored in a nested dictionary, we can use the del statement. The del statement lets you delete an object. del is written like a Python break statement, on its own line, followed by the item in the dictionary that you want to delete.
You could use numpy's array_split function e.g., np. array_split(np. array(data), 20) to split into 20 nearly equal size chunks.
Today we'll be talking about the nested list and dictionary. Nested lists and dictionaries are often used to better structure your data. Theoretically there are no limits to the depth of nesting and you can have a list inside another list, which is inside yet another list, which itself also is inside another list, etc.
use defaultdict
import collections result = collections.defaultdict(list) for d in dict_list: result[d['event']].append(d) result_list = result.values() # Python 2.x result_list = list(result.values()) # Python 3 This way, you don't have to make any assumptions about how many different events there are or if there are any events missing.
This gives you a list of lists. If you want a dict indexed by event, I would probably use dict(d) if you plan on doing any random access.
As far as constructing a bunch of individual lists, I think that that's a bad idea. It will necessitate creating them as globals or using eval (or getting hacky in some other way) unless you know exactly how many there are going to be which you claim not to. It's best to just keep them in a container.
56
This one is O(n log n) because of the sort, but I wouldn't worry too much unless there are a lot of items in the list.
It the list is already sorted by event, you can skip the sort of course.
>>> from operator import itemgetter >>> from itertools import groupby >>> d=[{'event': 0, 'voltage': 1, 'time': 0}, ... {'event': 0, 'voltage': 2, 'time': 1}, ... {'event': 1, 'voltage': 1, 'time': 2}, ... {'event': 1, 'voltage': 2, 'time': 3}, ... {'event': 2, 'voltage': 1, 'time': 4}, ... {'event': 2, 'voltage': 2, 'time': 5}] >>> groupby(sorted(d, key=itemgetter('event')), key=itemgetter('event')) <itertools.groupby object at 0xb78138c4> >>> for x in _: ... print x[0], list(x[1]) ... 0 [{'time': 0, 'event': 0, 'voltage': 1}, {'time': 1, 'event': 0, 'voltage': 2}] 1 [{'time': 2, 'event': 1, 'voltage': 1}, {'time': 3, 'event': 1, 'voltage': 2}] 2 [{'time': 4, 'event': 2, 'voltage': 1}, {'time': 5, 'event': 2, 'voltage': 2}] If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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