import numpy  as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots()
x = np.linspace(0, np.pi*4, 100)
y = np.cos(x) + np.sin(x)

ax.plot(x, y)
ax.spines.right.set_visible(False)
ax.spines.top.set_visible(False)
ax.spines.bottom.set_bounds(0, np.pi*4)