A have produced a boxplot with Facetgrid in seaborn the following way
# Import the dataset
tips = sns.load_dataset(\"tips\")
# Plot using Facegrid, separated by
You can get a list of axes used in the FacetGrid using FacetGrid.axes
which returns the axes used. You can then do all of the normal matplotlib operations using these axes, such as axhline for horizontal lines, or plt.text for putting text on the axes:
import seaborn as sns
import matplotlib.pyplot as plt
tips = sns.load_dataset("tips")
# Plot using Facegrid, separated by smoke
plt.style.use('ggplot')
g = sns.FacetGrid(tips, col="smoker", size=5, aspect=1.5)
g.map(sns.boxplot, "sex", "total_bill", palette='viridis', order=['Male', 'Female'])
ax1, ax2 = g.axes[0]
ax1.axhline(10, ls='--')
ax2.axhline(30, ls='--')
ax1.text(0.5,25, "Some text")
ax2.text(0.5,25, "Some text")
plt.show()