[python] Plotting a python dict in order of key values

I have a python dictionary that looks like this:

In[1]: dict_concentration
Out[2] : {0: 0.19849878712984576,
5000: 0.093917341754771386,
10000: 0.075060643507712022,
20000: 0.06673074282575861,
30000: 0.057119318961966224,
50000: 0.046134834546203485,
100000: 0.032495766396631424,
200000: 0.018536317451599615,
500000: 0.0059499290585381479}

They keys are type int, the values are type float64. Unfortunately, when I try to plot this with lines, matplotlib connects the wrong points (plot attached). How can I make it connect lines in order of the key values?

Python dictionaries are unordered. If you want an ordered dictionary, use collections.OrderedDict

In your case, sort the dict by key before plotting,

import matplotlib.pylab as plt

lists = sorted(d.items()) # sorted by key, return a list of tuples

x, y = zip(*lists) # unpack a list of pairs into two tuples

plt.plot(x, y)
plt.show()

Here is the result.

Simply pass the sorted items from the dictionary to the plot() function. concentration.items() returns a list of tuples where each tuple contains a key from the dictionary and its corresponding value.

You can take advantage of list unpacking (with *) to pass the sorted data directly to zip, and then again to pass it into plot():

import matplotlib.pyplot as plt

concentration = {
    0: 0.19849878712984576,
    5000: 0.093917341754771386,
    10000: 0.075060643507712022,
    20000: 0.06673074282575861,
    30000: 0.057119318961966224,
    50000: 0.046134834546203485,
    100000: 0.032495766396631424,
    200000: 0.018536317451599615,
    500000: 0.0059499290585381479}

plt.plot(*zip(*sorted(concentration.items())))
plt.show()

sorted() sorts tuples in the order of the tuple's items so you don't need to specify a key function because the tuples returned by dict.item() already begin with the key value.