More efficient matplotlib stacked bar chart - how to calculate bottom values

Question

I need some help making a set of stacked bar charts in python with matlibplot. My basic code is below but my problems is how to generate the value for bottom fo

Answer 1

[sum(values) for values in zip(a, b, c)]

In Python 2 you can also do

map(sum, zip(a, b, c))

but Python 3 would need

list(map(sum, zip(a, b, c)))

which is less nice.

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You could encapsulate this:

def sumzip(*items):
    return [sum(values) for values in zip(*items)]

and then do

p1 = plt.bar(ind, a, 1, color='#ff3333')
p2 = plt.bar(ind, b, 1, color='#33ff33', bottom=sumzip(a))
p3 = plt.bar(ind, c, 1, color='#3333ff', bottom=sumzip(a, b))
p4 = plt.bar(ind, d, 1, color='#33ffff', bottom=sumzip(a, b, c))

too.

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If a, b, c and d are numpy arrays you can also do sum([a, b, c]):

a = np.array([3,6,9])
b = np.array([2,7,1])
c = np.array([0,3,1])
d = np.array([4,0,3])

p1 = plt.bar(ind, a, 1, color='#ff3333')
p2 = plt.bar(ind, b, 1, color='#33ff33', bottom=sum([a]))
p3 = plt.bar(ind, c, 1, color='#3333ff', bottom=sum([a, b]))
p4 = plt.bar(ind, d, 1, color='#33ffff', bottom=sum([a, b, c]))