y2 = np.array([4, 3, 2])
y3 = np.array([1, 4, 1])
width = 0.5
handles = []
b1 = plt.bar(x, y1, color='#2040D0', width=width, linewidth=0)
handles.append(b1)
b2 = plt.bar(x, y2, bottom=y1, color='#60A0D0', width=width, linewidth=0)
handles.append(b2)
b3 = plt.bar(x, y3, bottom=y1 + y2, color='#A0D0D0', width=width, linewidth=0)
handles.append(b3)
for b in handles:
    b[1].set_linewidth(3)
plt.xlim(x[0] - 0.5 * width, x[-1] + 1.5 * width)
plt.xticks(x + 0.5 * width, ['A', 'B', 'C'])
plt.show()
python + matplotlib: how can I change the bar's line width for a single bar?