plot.py

import matplotlib.pyplot as plt

def myplot(x, y, **kwargs):
    plt.plot(x, y, **kwargs)
    plt.xlabel('X')
    plt.ylabel('Y')
    plt.title('My plot')
    plt.show()

x = [1, 3, 4, 5]
y = [3, 6, 9, 12]

myplot(x, y, color='orange', marker='s')

# you can use a dictionary as kwargs
d = {'color':'magenta', 'marker':'d'}

myplot(x, y, **d)