import matplotlib.pyplot as plt
import time


def plotVoltages(vList):
    if ~plt.fignum_exists(1):
        print("true")
        plt.ylabel("Voltage (V)")
        plt.xlabel("Cell Number")
        plt.bar(vList, [1,2,3,4])
        plt.show()
    else:
        plt.clf()
        plt.draw()
    return



x = [1, 2, 3, 4]
plotVoltages(x)
time.sleep(3)
plt.clf()
x = [4,3,2,1]
plotVoltages(x)