from random import randrange
import pandas as pd
import matplotlib.pyplot as plt
from matplotlib.widgets import Cursor

# https://stackoverflow.com/questions/21583965/matplotlib-cursor-value-with-two-axes
def make_format(current, other, data):
    # current and other are axes
    def format_coord(x, y):
        # x, y are data coordinates
        # convert to display coords
        display_coord = current.transData.transform((x,y))
        inv = other.transData.inverted()
        # convert back to data coords with respect to ax
        other_ax_data_coord = inv.transform(display_coord)
        return 'x: {:.1f}'.format(int(round(x))) + ', left y: {:.1f}'.format(other_ax_data_coord[1]) + ', s1: {:.1f}'.format(data.iloc[int(round(x)), 0]) + ', s2: {:.1f}'.format(data.iloc[int(round(x)), 1]) + ', right y: {:.1f}'.format(y)

    return format_coord

data = pd.DataFrame(dict(
    s1=[randrange(-1000, 1000) for _ in range(100)],
    s2=[randrange(-100, 100) for _ in range(100)],
    )).cumsum()
cols = data.columns

fig, ax_host = plt.subplots()

# Get default color style from pandas
colors = getattr(getattr(pd.plotting, '_style'), '_get_standard_colors')(num_colors=len(cols))

# First axis
ax_host = data.loc[:, cols[0]].plot( ax=ax_host, label=cols[0], color=colors[0])
ax_host.set_ylabel(ylabel=cols[0])
legend_handle_host, label_host = ax_host.get_legend_handles_labels()

# Second y-axis
ax_twinx = ax_host.twinx()
ax_twinx.spines['right'].set_position(('axes', 1))
line = data.loc[:, cols[1]].plot(ax=ax_twinx, label=cols[1], color=colors[1])
ax_twinx.set_ylabel(ylabel=cols[1])

# Proper legend position
legend_handle_twinx, label_twinx = ax_twinx.get_legend_handles_labels()
ax_host.legend(legend_handle_host+legend_handle_twinx, label_host+label_twinx, loc=0)

crosshair = Cursor(ax_twinx, useblit=True, color='black', linewidth=1)

ax_twinx.format_coord = make_format(ax_twinx, ax_host, data)

plt.show(block=True)