Python list of Dictionaries, sort and print values by chronological order

Question

I have a list containing multiple dictionaries. Each Dictionary will have a date and time Key. What I am trying to figure out is how print the values of each dictionary to a line in chronological order.

Below is an example of my code.

list_of_dicts = []

dict1 = {'Source': 'Log1', 'Type': 'Connection', 'Datetime': '2014-02-13 14:10:00', 'fullpath':'N/A'}
dict2 = {'Source': 'Log2', 'Type': 'Disconnect', 'Datetime': '2014-05-13 11:00:00', 'fullpath':'N/A'}
dict3 = {'Source': 'Log4', 'Type': 'Other', 'Datetime': '2014-05-10 02:50:00', 'fullpath':'N/A'}

list_of_dicts.append(dict1)
list_of_dicts.append(dict2)
list_of_dicts.append(dict3)

The expected output would look like this:

Datetime                Source  Type        Fullpath
2014-02-13 14:10:00     Log1    Connection  N/A
2014-05-10 02:50:00     Log4    Other       N/A
2014-05-13 11:00:00     Log2    Disconnect  N/A

I would greatly appreciate anyone's guidance on this. Thanks so much.

Answer 1

Your dates are formatted using the ISO8601 format, making them lexicographically sortable.

Just sort your list on the Datetime key of each dictionary:

from operator import itemgetter

for entry in sorted(list_of_dicts, key=itemgetter('Datetime')):
    # format your output

Demo:

>>> list_of_dicts = [
...     {'Source': 'Log1', 'Type': 'Connection', 'Datetime': '2014-02-13 14:10:00', 'fullpath':'N/A'},
...     {'Source': 'Log2', 'Type': 'Disconnect', 'Datetime': '2014-05-13 11:00:00', 'fullpath':'N/A'},
...     {'Source': 'Log4', 'Type': 'Other', 'Datetime': '2014-05-10 02:50:00', 'fullpath':'N/A'},
... ]
>>> from operator import itemgetter
>>> for entry in sorted(list_of_dicts, key=itemgetter('Datetime')):
...     print entry
... 
{'Source': 'Log1', 'fullpath': 'N/A', 'Type': 'Connection', 'Datetime': '2014-02-13 14:10:00'}
{'Source': 'Log4', 'fullpath': 'N/A', 'Type': 'Other', 'Datetime': '2014-05-10 02:50:00'}
{'Source': 'Log2', 'fullpath': 'N/A', 'Type': 'Disconnect', 'Datetime': '2014-05-13 11:00:00'}

Answer 2

Use http://docs.python.org/2/library/functions.html#sorted with a lambda function. It works for more deeply nested dictionaries as well.

sorted_entries = sorted(list_of_dicts,key=lambda x:x['Datetime'])

Answer 3

I did not take the time to format things pretty for you, but here is a quick and dirty way to sort these. Since your dates are formatted in a nice way, they can be sorted easily. This is not as efficient as the other answers, because I am constructing a whole new dictionary with redundant data.

list_of_dicts = []

dict1 = {'Source': 'Log1', 'Type': 'Connection', 'Datetime': '2014-02-13 14:10:00', 'fullpath':'N/A'}
dict2 = {'Source': 'Log2', 'Type': 'Disconnect', 'Datetime': '2014-05-13 11:00:00', 'fullpath':'N/A'}
dict3 = {'Source': 'Log4', 'Type': 'Other', 'Datetime': '2014-05-10 02:50:00', 'fullpath':'N/A'}

list_of_dicts.append(dict1)
list_of_dicts.append(dict2)
list_of_dicts.append(dict3)

d = {d['Datetime']:d for d in list_of_dicts} # dictionary comprehension

for k in sorted(d.keys()):
    print(d[k])