Add minor gridlines to matplotlib plot using seaborn

Question

I'm a fan of the Seaborn package for making nice-looking plots using Matplotlib. But I can't seem to figure out how to show minor gridlines in my plots.

import numpy as np
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.grid(b=True, which='major')
ax.grid(b=True, which='minor')

gives:

Any thoughts here? Also any thoughts on how to adjust the style of the Seaborn gridlines that do show up...in particular, I'd love to make them narrower.

Answer 1

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)

Answer 2

That's because the minor ticks are not yet defined, so we need to add for example:

ax.set_xticks(np.arange(0,8)-0.5, minor=True)
ax.set_yticks([-1.25, -0.75, -0.25,0.24,0.75,1.25], minor=True)