Add minor gridlines

Wound up combining CT Zhu’s answer with tcaswell’s hint:

import numpy as np
import matplotlib as mpl
import matplotlib.pyplot as plt
import seaborn as sbn

x = np.linspace(0, 2 * np.pi, 100)
y = np.sin(x)

fig, ax = plt.subplots(1, 1)

ax.scatter(x, y)
ax.get_xaxis().set_minor_locator(mpl.ticker.AutoMinorLocator())
ax.get_yaxis().set_minor_locator(mpl.ticker.AutoMinorLocator())
ax.grid(b=True, which="major", color="w", linewidth=1.0)
ax.grid(b=True, which="minor", color="w", linewidth=0.5)