Examples
Using df.boxplot() Boxplots can be created for every column in the dataframe:

import numpy as np
import pandas as pd

np.random.seed(2345)
df = pd.DataFrame(np.random.randn(20,4),
                  columns=['C1', 'C2', 'C3', 'C4'])
boxplot = df.boxplot(column=['C1', 'C2', 'C3'])

Boxplots of variables distributions grouped by the values of a third variable:

df = pd.DataFrame(np.random.randn(20, 2),
                  columns=['C1', 'C2'])
df['X'] = pd.Series(['P', 'P', 'P', 'P', 'P',
                     'Q', 'Q', 'Q', 'Q', 'Q'])
boxplot = df.boxplot(by='X')

A list of strings (i.e. ['X', 'Y']) can be passed to boxplot in order to group the data
by combination of the variables in the x-axis:

df = pd.DataFrame(np.random.randn(20,3),
                  columns=['C1', 'C2', 'C3'])
df['X'] = pd.Series(['P', 'P', 'P', 'P', 'P',
                     'Q', 'Q', 'Q', 'Q', 'Q'])
df['Y'] = pd.Series(['P', 'P', 'P', 'P', 'P',
                     'Q', 'P', 'Q', 'P', 'Q'])
boxplot = df.boxplot(column=['C1', 'C2'], by=['X', 'Y'])

The layout of boxplot can be adjusted giving a tuple to layout:

boxplot = df.boxplot(column=['C1', 'C2'], by='X',
                     layout=(2, 1))

Additional formatting can be done to the boxplot:

boxplot = df.boxplot(grid=False, rot=55, fontsize=25)

The parameter return_type can be used to select the type of element returned by boxplot.
When return_type='axes' is selected, the matplotlib axes on which the boxplot is drawn are returned:

boxplot = df.boxplot(column=['C1','C2'], return_type='axes')
type(boxplot)

matplotlib.axes._subplots.AxesSubplot

When grouping with by, a Series mapping columns to return_type is returned:

boxplot = df.boxplot(column=['C1', 'C2'], by='X',
                     return_type='axes')
type(boxplot)

pandas.core.series.Series

If return_type is None, a NumPy array of axes with the same shape
as layout is returned:

boxplot =  df.boxplot(column=['C1', 'C2'], by='X',
                      return_type=None)
type(boxplot)

numpy.ndarray