Python ipywidgets: create a savefig button

Question

I am trying to create a button from ipywidgets.Button instance that will save a specific figure once it's pressed. But using the following Ipython notebook leads to multiple file savings once the button has been hit:

import numpy as np
from ipywidgets import interact, interactive,FloatSlider,IntSlider,Button
from IPython.display import display
import matplotlib.pylab as plt
%matplotlib inline
button = Button(description="Savefig")
display(button)
def plotfields(p,a):
    fig,ax = plt.subplots(1,2,figsize=(4*2,4),sharey=True)
    X,Y=np.meshgrid(np.linspace(0,100,100),np.linspace(0,100,100))
    b1 = np.sin(p*X)*np.cos(a*Y)
    b2 = np.sin(a*X)*np.cos(p*Y)
    ax[0].imshow(b1,aspect='auto')
    ax[1].imshow(b2,aspect='auto')
    ax[0].set_ylabel(r'$t$')
    ax[0].set_xlabel(r'$x$')
    ax[1].set_xlabel(r'$x$')
    plt.tight_layout()
    def on_button_clicked(b):
        fig.savefig("test_p{:.3s}_a{:.3s}.eps".format(str(int(100*p)),str(int(100*a))))
        fig.savefig("test_p{:.3s}_a{:.3s}.png".format(str(int(100*p)),str(int(100*a))))
    button.on_click(on_button_clicked)

p_w  = FloatSlider(min=0.01, max=1, step=0.01, value=0.01)
a_w  = FloatSlider(min=0.01, max=1, step=0.01, value=0.01)
interact(plotfields,p=p_w,a=a_w)

ImportanceOfBeingErnest · Accepted Answer · 2018-01-21 11:35:17Z

3

The problem is that you create one callback for each time the plotfields function is called; and it is called a lot of times, everytime one of the sliders is moved.
It would therefore make sense to move the button.on_click(on_button_clicked) outside of the repeatedly called function.
I would then use display to display the figure.

%%capture
import numpy as np
from ipywidgets import interact, interactive,FloatSlider,IntSlider,Button
from IPython.display import display
import matplotlib.pylab as plt
%matplotlib inline
button = Button(description="Savefig")
display(button)

params = [0.01,0.01]

def init():
    fig,ax = plt.subplots(1,2,figsize=(4*2,4),sharey=True)
    X,Y=np.meshgrid(np.linspace(0,100,100),np.linspace(0,100,100))
    b1 = np.sin(params[0]*X)*np.cos(params[1]*Y)
    b2 = np.sin(params[1]*X)*np.cos(params[0]*Y)
    im1 = ax[0].imshow(b1,aspect='auto')
    im2 = ax[1].imshow(b2,aspect='auto')
    ax[0].set_ylabel(r'$t$')
    ax[0].set_xlabel(r'$x$')
    ax[1].set_xlabel(r'$x$')
    plt.tight_layout()
    return fig, im1, im2

fig, im1, im2 = init();

def plotfields(p,a):
    params[0] = p; params[1] = a
    b1 = np.sin(params[0]*X)*np.cos(params[1]*Y)
    b2 = np.sin(params[1]*X)*np.cos(params[0]*Y)
    im1.set_data(b1)
    im2.set_data(b2)
    display(fig)

def on_button_clicked(b):
    fig.savefig("test_p{:.3s}_a{:.3s}.eps".format(str(int(100*params[0])),str(int(100*params[1]))))
    fig.savefig("test_p{:.3s}_a{:.3s}.png".format(str(int(100*params[0])),str(int(100*params[1]))))
button.on_click(on_button_clicked)

p_w  = FloatSlider(min=0.01, max=1, step=0.01, value=0.01)
a_w  = FloatSlider(min=0.01, max=1, step=0.01, value=0.01)
interact(plotfields,p=p_w,a=a_w)

answered Jan 21, 2018 at 11:35

ImportanceOfBeingErnest

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1 Comment

hc_dev Over a year ago

@kommandoking: Saw your addition of X,Y inside method plotfields(p,a): Well intended, but that code-correction should be fist put as comment. You don't know about author's intent. Give them a chance to fix it their own or explain it.

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