import warnings is a Python import that issues warning messages. Use it to alert users about deprecated features or suspicious code without raising exceptions.

# Python
# description: issue and filter warnings
 
import warnings
 
# Issue a warning
warnings.warn("This feature is deprecated", DeprecationWarning)
 
# Suppress warnings temporarily
with warnings.catch_warnings():
    warnings.simplefilter("ignore")
    # Code that issues warnings runs silently
    warnings.warn("This warning is suppressed")
 
# Filter warnings globally
warnings.simplefilter("always")  # show all warnings
warnings.simplefilter("ignore")  # ignore all warnings
warnings.simplefilter("error")   # convert to exceptions
 
# Custom warning category
class CustomWarning(UserWarning):
    pass
 
warnings.warn("Custom issue", CustomWarning)

• warnings.warn(message, category): issue warning
• warnings.simplefilter(action): filter warnings
  • “always” — always print
  • “ignore” — suppress
  • “error” — convert to exception
  • “once” — print once per location
• warnings.catch_warnings(): context manager for temporary filtering
• Warning categories: UserWarning, DeprecationWarning, SyntaxWarning