How to add percentages on top of bars in seaborn?

Answer is inspire from jrjc and cphlewis answer as above but more simple and understandable

sns.set(style="whitegrid")
plt.figure(figsize=(8,5))
total = float(len(train_df))
ax = sns.countplot(x="event", hue="event", data=train_df)
plt.title('Data provided for each event', fontsize=20)
for p in ax.patches:
    percentage = '{:.1f}%'.format(100 * p.get_height()/total)
    x = p.get_x() + p.get_width()
    y = p.get_height()
    ax.annotate(percentage, (x, y),ha='center')
plt.show()

The seaborn.catplot organizing function returns a FacetGrid, which gives you access to the fig, the ax, and its patches. If you add the labels when nothing else has been plotted you know which bar-patches came from which variables. From @LordZsolt's answer I picked up the order argument to catplot: I like making that explicit because now we aren't relying on the barplot function using the order we think of as default.

import seaborn as sns
from itertools import product

titanic = sns.load_dataset("titanic")

class_order = ['First','Second','Third'] 
hue_order = ['child', 'man', 'woman']
bar_order = product(class_order, hue_order)

catp = sns.catplot(data=titanic, kind='count', 
                   x='class', hue='who',
                   order = class_order, 
                   hue_order = hue_order )

# As long as we haven't plotted anything else into this axis,
# we know the rectangles in it are our barplot bars
# and we know the order, so we can match up graphic and calculations:

spots = zip(catp.ax.patches, bar_order)
for spot in spots:
    class_total = len(titanic[titanic['class']==spot[1][0]])
    class_who_total = len(titanic[(titanic['class']==spot[1][0]) & 
        (titanic['who']==spot[1][1])])
    height = spot[0].get_height() 
    catp.ax.text(spot[0].get_x(), height+3, '{:1.2f}'.format(class_who_total/class_total))

    #checking the patch order, not for final:
    #catp.ax.text(spot[0].get_x(), -3, spot[1][0][0]+spot[1][1][0])

produces

An alternate approach is to do the sub-summing explicitly, e.g. with the excellent pandas, and plot with matplotlib, and also do the styling yourself. (Though you can get quite a lot of styling from sns context even when using matplotlib plotting functions. Try it out -- )

with_hue function will plot percentages on the bar graphs if you have the 'hue' parameter in your plots. It takes the actual graph, feature, Number_of_categories in feature, and hue_categories(number of categories in hue feature) as a parameter.

without_hue function will plot percentages on the bar graphs if you have a normal plot. It takes the actual graph and feature as a parameter.

def with_hue(ax, feature, Number_of_categories, hue_categories):
    a = [p.get_height() for p in ax.patches]
    patch = [p for p in ax.patches]
    for i in range(Number_of_categories):
        total = feature.value_counts().values[i]
        for j in range(hue_categories):
            percentage = '{:.1f}%'.format(100 * a[(j*Number_of_categories + i)]/total)
            x = patch[(j*Number_of_categories + i)].get_x() + patch[(j*Number_of_categories + i)].get_width() / 2 - 0.15
            y = patch[(j*Number_of_categories + i)].get_y() + patch[(j*Number_of_categories + i)].get_height() 
            ax.annotate(percentage, (x, y), size = 12)

def without_hue(ax, feature):
    total = len(feature)
    for p in ax.patches:
        percentage = '{:.1f}%'.format(100 * p.get_height()/total)
        x = p.get_x() + p.get_width() / 2 - 0.05
        y = p.get_y() + p.get_height()
        ax.annotate(percentage, (x, y), size = 12)