[ Python 常見問題 ] matplotlib - How to force the Y axis to only use integers in Matplotlib?

Source From Here 
Question 
I'm plotting a histogram using the matplotlib.pyplot module and I am wondering how I can force the y-axis labels to only show integers (e.g. 0, 1, 2, 3 etc.) and not decimals (e.g. 0., 0.5, 1., 1.5, 2. etc.). 

How-To 
If you have the y-data 

view plaincopy to clipboardprint?

1. y = [0., 0.5, 1., 1.5, 2., 2.5]  

You can use the maximum and minimum values of this data to create a list of natural numbers in this range. For example: 

view plaincopy to clipboardprint?

1. import math  
2. print range(math.floor(min(y)), math.ceil(max(y))+1)  

which will yield: 

view plaincopy to clipboardprint?

1. [0, 1, 2, 3]  

You can then set the y tick mark locations (and labels) using matplotlib.pyplot.yticks: 

view plaincopy to clipboardprint?

1. yint = range(min(y), math.ceil(max(y))+1)  
2.   
3. matplotlib.pyplot.yticks(yint)  

For example, we have sample code below: 

view plaincopy to clipboardprint?

1. import matplotlib.pyplot as plt    
2. import numpy as np  
3. import math  
4.   
5. x = np.linspace(0, 10, 6)    
6. y = np.array([0., 0.5, 1., 1.5, 2., 2.5])    
7. print("y={}".format(y))  
8.   
9. fig, ax = plt.subplots()  
10.   
11. plt.plot(x, y)    
12.   
13. plt.xlabel('time')    
14. plt.ylabel('Some function of time')    
15. plt.title("My cool chart")    
16.   
17. plt.show()  

With above suggestion, you can have new version below: 

view plaincopy to clipboardprint?

1. import matplotlib.pyplot as plt    
2. import numpy as np  
3. import math  
4.   
5. x = np.linspace(0, 10, 6)    
6. y = np.array([0., 0.5, 1., 1.5, 2., 2.5])    
7. print("y={}".format(y))  
8.   
9. fig, ax = plt.subplots()  
10.   
11. plt.plot(x, y)    
12.   
13. plt.xlabel('time')    
14. plt.ylabel('Some function of time')    
15. plt.title("My cool chart")    
16.   
17. # Modify ytick labels  
18. print("min={}; max={}".format(math.floor(min(y.tolist())), math.ceil(max(y.tolist()))))  
19. yint = range(math.floor(min(y.tolist())), math.ceil(max(y.tolist()))+1)  
20. plt.yticks(yint)  
21.   
22. plt.show()  

You can achieve your goal: 

Supplement 
* FAQ - Modify tick label text