warn() is used to generate the warnings. Now, we will see a simple example of generating warnings. Write a script called generate_warnings.py and write a following code in it:

import warnings
warnings.simplefilter('error', UserWarning)
print('Before')
warnings.warn('Write your warning message here')
print('After')

Run the script as follows:

$ python3 generate_warnings.py

Output:
Before:
Traceback (most recent call last):
  File "generate_warnings.py", line 6, in <module>
    warnings.warn('Write your warning message here')
UserWarning: Write your warning message here

In the preceding script, we passed a warning message through warn(). We used a simple filter so that your warning will get treated as an error and that error will get solved accordingly by the programmer.