Matplotlib.ticker.FuncFormatter class in Python

Matplotlib is an amazing visualization library in Python for 2D plots of arrays. Matplotlib is a multi-platform data visualization library built on NumPy arrays and designed to work with the broader SciPy stack.

matplotlib.ticker.FuncFormatter

The matplotlib.ticker.FuncFormatter class uses a user defined function for formatting. This user defined function must take two values as inputs for a tick value x and a position pos. 

Syntax: class matplotlib.ticker.FuncFormatter(func)
Parameter: 

• func: The user defined function for formatting of the plot. 
  

Example 1:

Python3

import matplotlib.pyplot as plt
import matplotlib.ticker as tick
import numpy as np


x = np.linspace(0, 10, 1000)
y = 0.000001 * np.sin(10 * x)

fig = plt.figure()
ax = fig.add_subplot(111)

ax.plot(x, y)

def y_fmt(x, y):
    return '{:2.2e}'.format(x).replace('e', 'x10^')

ax.yaxis.set_major_formatter(tick.FuncFormatter(y_fmt))

plt.show()

Output:

Example 2:

Python3

import matplotlib.pyplot as plt
from matplotlib.ticker import FuncFormatter


fig, ax = plt.subplots()
ax.axis([0.01, 10000, 1, 1000000])
ax.loglog()

for axis in [ax.xaxis, ax.yaxis]:
    formatter = FuncFormatter(lambda y, _: '{:.16g}'.format(y))
    axis.set_major_formatter(formatter)

plt.show()

Output: