plotting all keys of a dictionary which contains list as values (python)

Question

In python 2.7, I have a dictionary whose size can vary. For each key, Q1,Q2,Q3.... I need to plot the dictionary values, which are lists containing dates and integers.

{'Q1': [['20.03.2016', 25], ['21.03.2016', 35], ['22.03.2016', 22], ['23.03.2016
', 50], ['24.03.2016', 50], ['30.03.2016', 50], ['30.03.2016', 50]], 'Q3': [['20
.03.2016', 23], ['21.03.2016', 21], ['22.03.2016', 27], ['23.03.2016', 20], ['24
.03.2016', 20], ['30.03.2016', 20], ['30.03.2016', 20]], 'Q2': [['20.03.2016', 1
5], ['21.03.2016', 12], ['22.03.2016', 15], ['23.03.2016', 15], ['24.03.2016', 1
5], ['30.03.2016', 15], ['30.03.2016', 15]], 'Q5': [['20.03.2016', 320], ['21.03
.2016', 30], ['22.03.2016', 30], ['23.03.2016', 30], ['24.03.2016', 30], ['30.03
.2016', 30], ['30.03.2016', 30]], 'Q4': [['20.03.2016', 130], ['21.03.2016', 10]
, ['22.03.2016', 10], ['23.03.2016', 10], ['24.03.2016', 10], ['30.03.2016', 10]
, ['30.03.2016', 10]], 'Q7': [['23.03.2016', 5], ['24.03.2016', 5], ['30.03.2016
', 5], ['30.03.2016', 5]], 'Q9': [['30.03.2016', 17]], 'Q8': [['24.03.2016', 15]
, ['30.03.2016', 15], ['30.03.2016', 15]]}

How can I draw all the keys in one plot window containing lines for each key and labelled as per key names itself? Each line should be color coded and show all the integer vs date data points for each key. So Q1 line will plot second colomn(integers) vs first colomn (dates)

['20.03.2016', 25], 
['21.03.2016', 35],
['22.03.2016', 22],
['23.03.2016', 50],
['24.03.2016', 50], 
['30.03.2016', 50],
['30.03.2016', 50]

Each line can be color coded and should be have label of the key in the legend. I am using numpy and matplotlib libraries in python.

could you rephrase your question a bit? I was thinking, will it work for you if you create a date by number plot where each key is represented by a color? — jtitusj
– jtitusj, Commented Mar 30, 2016 at 15:46
@John, Yes, you got it right. Each key should be color coded. So for each key, it should plot list[1] vs list[0] (the two colomns in the list) — Sha
– Sha, Commented Mar 30, 2016 at 16:08
Mirror question: Plot data stored in list of dicts using list comprehension — Kevin Chou
– Kevin Chou, Commented Aug 19, 2020 at 12:38

Hannes Ovrén · Accepted Answer · 2016-03-30 16:17:08Z

1

We can simply iterate over the dictionary items, and then use zip() to unpack the values. The label= keyword argument to plot() will make the legend() call create the legend automatically.

for key, data_list in data_dict.items():
    dates_str, values = zip(*data_list)  # Unpack
    dates = convert_str_to_dates(dates_str)  # Not handled in example
    plt.plot(dates, values, label=key)
plt.legend()

To be solved is how to go from a list of strings to some sort of date object that matplotlib understands. This should be fairly easy to find in the documentation though.

Edit: The trick with using zip() to unpack a list-of-lists was one of those "Aha!"-moments for me :)

answered Mar 30, 2016 at 16:17

Hannes Ovrén

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1 Comment

Sha Over a year ago

Thanks! Thats perfect! I used dates = [dt.datetime.strptime(d,'%d.%m.%Y').date() for d in dates_str] for handling dates in strings.

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