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 :

# 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 :

python-matplotlib-callback

Example 2 :

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() 