You can use one of the following methods to adjust the bin size of histograms in Matplotlib:

Method 1: Specify Number of Bins

plt.hist(data, bins=6)

Method 2: Specify Bin Boundaries

plt.hist(data, bins=[0, 4, 8, 12, 16, 20])

Method 3: Specify Bin Width

w=2
plt.hist(data, bins=np.arange(min(data), max(data) + w, w))

The following examples show how to use each of these methods in practice.

Example 1: Specify Number of Bins

The following code shows how to specify the number of bins to use in a histogram:

import matplotlib.pyplotas plt

#define data
data = [1, 2, 2, 4, 5, 5, 6, 8, 9, 12, 14, 15, 15, 15, 16, 17, 19]

#create histogram with specific number of bins
plt.hist(data, edgecolor='black', bins=6) 

Keep in mind that the more bins you specify, the more narrow the bins will be.

Example 2: Specify Bin Boundaries

The following code shows how to specify the actual bin boundaries in a histogram:

import matplotlib.pyplotas plt

#define data
data = [1, 2, 2, 4, 5, 5, 6, 8, 9, 12, 14, 15, 15, 15, 16, 17, 19]

#create histogram with specific bin boundaries
plt.hist(data, edgecolor='black', bins=[0, 4, 8, 12, 16, 20])

Example 3: Specify Bin Width

The following code shows how to specify the bin width in a histogram:

import matplotlib.pyplotas plt
import numpy as np

#define data
data = [1, 2, 2, 4, 5, 5, 6, 8, 9, 12, 14, 15, 15, 15, 16, 17, 19]

#specify bin width to use
w=2
#create histogram with specified bin width
plt.hist(data, edgecolor='black', bins=np.arange(min(data), max(data) + w, w)) 

Keep in mind that the smaller the bin width you specify, the more narrow the bins will be.

The following tutorials explain how to perform other common functions in Matplotlib: