assert keyword in python

1assert <condition>,<error message>
2#The assert condition must always be True, else it will stop execution and return the error message in the second argument
3assert 1==2 , "Not True" #returns 'Not True' as Assertion Error.

1The assert keyword is used when debugging code.
2
3The assert keyword lets you test if a condition in your code returns 
4True, if not, the program will raise an AssertionError.
5
6You can write a message to be written if the code returns False, check 
7the example below.
8
9x = "hello"
10
11#if condition returns False, AssertionError is raised:
12assert x == "goodbye", "x should be 'hello'"

1def input_age(age):
2   try:
3       assert int(age) > 18
4   except ValueError:
5       return 'ValueError: Cannot convert into int'
6   else:
7       return 'Age is saved successfully'
8 
9print(input_age('23'))  	# This will print
10print(input_age(25))  		# This will print
11print(input_age('nothing')) # This will raise ValueError which is handled
12print(input_age('18'))  	# This will raise AssertionError, program collapses
13print(input_age(43))  		# This won't print

1assert False, "Oh no! This assertion failed!"