Matplotlib.pyplot.connect() in Python

Last Updated : 03 May, 2020

Matplotlib is a library in Python and it is numerical - mathematical extension for NumPy library. Pyplot is a state-based interface to a Matplotlib module which provides a MATLAB-like interface.

matplotlib.pyplot.connect() Function

This method is used to connect an event with string s to a function.

Syntax: matplotlib.pyplot.connect(s, func) Parameters: This method accept the following parameters that are described below: s(str): One of the following events ids: 1. 'button_press_event' 2. 'button_release_event' 3. 'draw_event' 4. 'key_press_event' 5. 'key_release_event' 6. 'motion_notify_event' 7. 'pick_event' 8. 'resize_event' 9. 'scroll_event' 10. 'figure_enter_event', 11. 'figure_leave_event', 12. 'axes_enter_event', 13. 'axes_leave_event' 14. 'close_event'. func(callable): The callback function to be executed, which must have the signature: def func(event: Event) -> Any Returns(cid): A connection id that can be used with FigureCanvasBase.mpl_disconnect.

Example 1 :

Python3 1==

# matplotlib.pyplot.connect()
from matplotlib.backend_bases import MouseButton
import matplotlib.pyplot as plt
import numpy as np


t = np.arange(0.0, 1.0, 0.01)
s = np.sin(2 * np.pi * t)
fig, ax = plt.subplots()
ax.plot(t, s)


def on_move(event):
    
    # get the x and y pixel coords
    x, y = event.x, event.y
    
    if event.inaxes:
        ax = event.inaxes  # the axes instance
        print('data coords % f % f' % (event.xdata,
                                       event.ydata))


def on_click(event):
    
    if event.button is MouseButton.LEFT:
        print('disconnecting callback')
        plt.disconnect(binding_id)


binding_id = plt.connect('motion_notify_event',
                         on_move)

plt.connect('button_press_event', on_click)

plt.show()

Output :

Example 2 :

Python3 1==

from matplotlib.widgets import RectangleSelector
import numpy as np
import matplotlib.pyplot as plt


def line_select_callback(eclick, erelease):
    
    # Callback for line selection.
    # *eclick * and * erelease *
    # are the press and release events.
    x1, y1 = eclick.xdata, eclick.ydata
    x2, y2 = erelease.xdata, erelease.ydata
    print("(% 3.2f, % 3.2f) --> (% 3.2f, % 3.2f)" % (x1, y1, x2, y2))
    print(" The button you used were: % s % s" % (eclick.button, 
                                                  erelease.button))


def toggle_selector(event):
    
    print(' Key pressed.')
    
    if event.key in ['Q', 'q'] and toggle_selector.RS.active:
        print(' RectangleSelector deactivated.')
        toggle_selector.RS.set_active(False)
        print(' RectangleSelector activated.')
        toggle_selector.RS.set_active(True)


# make a new plotting range
fig, current_ax = plt.subplots()

# If N is large one can see
N = 100000

# improvement by use blitting ! 
# plt.plot(x, +np.sin(.2 * np.pi * x), 
# lw = 3.5, c ='b', alpha =.7)  
# plot something
x = np.linspace(0.0, 10.0, N)
plt.plot(x, +np.cos(.2 * np.pi * x), 
         lw = 3.5, c ='c', alpha =.5)
plt.plot(x, -np.sin(.2 * np.pi * x), 
         lw = 3.5, c ='r', alpha =.3)

print("\n      click  -->  release")

# drawtype is 'box' or 'line' or 'none'
toggle_selector.RS = RectangleSelector(current_ax, line_select_callback,
                                       drawtype ='box',
                                       useblit = True,
                                       button =[1, 3],  # don't use middle button
                                       minspanx = 5, minspany = 5,
                                       spancoords ='pixels',
                                       interactive = True)

plt.connect('key_press_event', toggle_selector)
plt.show()