Matplotlib: plotting with x-ticks labels

plot.py

def plot(keys: list, vals: list):
    import matplotlib.pyplot as plt

    fig = plt.figure()
    ax = fig.add_subplot(111)
    x = range(len(vals))
    ax.set_xticks(x) # plot every tick
    ax.set_xticklabels(keys, rotation=90)
    ax.plot(x, vals)
    fig.savefig('output.png', bbox_inches='tight') # bbox_inches='tight' to prevent text-overflow out of the frame