Change matplotlib.slider label text size

Question

I want to make plots and change their properties with slider. But the label text of matplotlib.widgets.Slider is very small for my eyes. I surfed the internet to find the answer how to change it, but I had no luck.

The crucial part of code is:

E0_slider_ax = fig.add_axes([0.6, 0.2, 0.25, 0.03], axisbg=axis_color)
E0_slider = mw.Slider(E0_slider_ax, r'$\epsilon_0$', 1,  100, valinit = E0)
# I want to make r'$\epsilon_0$' bigger

I tried to make text for the label as folows:

t = matplotlib.text.Text(r'$\epsilon_0$', size = 22)
E0_slider = mw.Slider(E0_slider_ax, label = t, valmin = 1, valmax = 100, valinit = E0)

but it returns me an error:

Traceback (most recent call last):

  File "<ipython-input-53-2310b0749547>", line 1, in <module>
    runfile('C:/Users/Robert/Desktop/multidif_S.py', 
wdir='C:/Users/Robert/Desktop')

  File "C:\Users\Robert\Desktop\WinPython-64bit-3.5.2.2\python-
3.5.2.amd64\lib\site-
packages\spyderlib\widgets\externalshell\sitecustomize.py", line 845, in 
runfile
    execfile(filename, namespace)

  File "C:\Users\Robert\Desktop\WinPython-64bit-3.5.2.2\python-
3.5.2.amd64\lib\site-
packages\spyderlib\widgets\externalshell\sitecustomize.py", line 103, in 
execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "C:/Users/Robert/Desktop/multidif_S.py", line 64, in <module>
    E0_slider = mw.Slider(E0_slider_ax, label = t, valmin = 1, valmax = 100, 
valinit = E0)

  File "C:\Users\Robert\Desktop\WinPython-64bit-3.5.2.2\python-
3.5.2.amd64\lib\site-packages\matplotlib\widgets.py", line 376, in __init__
    horizontalalignment='right')

  File "C:\Users\Robert\Desktop\WinPython-64bit-3.5.2.2\python-
3.5.2.amd64\lib\site-packages\matplotlib\axes\_axes.py", line 623, in text
    x=x, y=y, text=s)

  File "C:\Users\Robert\Desktop\WinPython-64bit-3.5.2.2\python-
3.5.2.amd64\lib\site-packages\matplotlib\text.py", line 220, in __init__
    self.set_text(text)

  File "C:\Users\Robert\Desktop\WinPython-64bit-3.5.2.2\python-
3.5.2.amd64\lib\site-packages\matplotlib\text.py", line 1206, in set_text
    self._text = '%s' % (s,)

  File "C:\Users\Robert\Desktop\WinPython-64bit-3.5.2.2\python-
3.5.2.amd64\lib\site-packages\matplotlib\text.py", line 186, in __str__
    return "Text(%g,%g,%s)" % (self._x, self._y, repr(self._text))

TypeError: a float is required

thx for help!

Answer 1

You cannot supply a text to the label argument. But you can change the label size afterwards. The label is available as Slider.label and, being a matplotlib.text.Text instance, can be changed in size using set_size.

import matplotlib.pyplot as plt
import matplotlib.widgets

fig = plt.figure()

E0_slider_ax = fig.add_axes([0.6, 0.2, 0.25, 0.03], facecolor="skyblue")
E0_slider =  matplotlib.widgets.Slider(E0_slider_ax, r'$\epsilon_0$', 1,  100, valinit = 50)
E0_slider.label.set_size(40)

plt.show()