Python | assert keyword
Assertions in any programming language are the debugging tools which help in smooth flow of code. Assertions are mainly assumptions that a programmer knows always wants to be true and hence puts them in code so that failure of them doesn’t allow the code to execute further.
In python assert keyword helps in achieving this task. This statement simply takes input a boolean condition, which when returns true doesn’t return anything, but if it is computed to be false, then it raises an AssertionError along with the optional message provided.
Syntax : assert condition, error_message(optional)
Parameters :
condition : The boolean condition returning true or false.
error_message : The optional argument to be printed in console in case ofAssertionErrorReturns :
ReturnsAssertionError, in case the condition evaluates to false along with the error message which when provided.
# Python 3 code to demonstrate # working of assert # initializing number a = 4b = 0 # using assert to check for 0 print ("The value of a / b is : ") assert b != 0, "Divide by 0 error"print (a / b) |
chevron_right
filter_none
Output :
The value of a/b is :
Runtime Exception :
Traceback (most recent call last):
File "/home/40545678b342ce3b70beb1224bed345f.py", line 10, in
assert b != 0, "Divide by 0 error"
AssertionError: Divide by 0 error
Practical Application : This has a much greater utility in testing and Quality assurance role in any development domain. Different types of assertions are used depending upon the application. Below is the simpler demonstration of program that only allows only the batch with all hot food to be dispatched, else rejects whole batch.
# Python 3 code to demonstrate # working of assert # Application # initializing list of foods temperatures batch = [ 40, 26, 39, 30, 25, 21] # initializing cut temperature cut = 26 # using assert to check for temperature greater than cut for i in batch: assert i >= 26, "Batch is Rejected" print (str(i) + " is O.K" ) |
chevron_right
filter_none
Output :
40 is O.K 26 is O.K 39 is O.K 30 is O.K
Runtime Exception :
Traceback (most recent call last):
File "/home/bd45fb65343814a85b6c19bbe366b419.py", line 13, in
assert i >= 26, "Batch is Rejected"
AssertionError: Batch is Rejected
Recommended Posts:
- Python | yield Keyword
- Global keyword in Python
- finally keyword in Python
- Python program to check if a given string is Keyword or not
- Python | Passing dictionary as keyword arguments
- How to check if a string is a valid keyword in Python?
- Python | Merge Python key values to list
- Important differences between Python 2.x and Python 3.x with examples
- Python | Index of Non-Zero elements in Python list
- Reading Python File-Like Objects from C | Python
- Python | Convert list to Python array
- Python | Add Logging to a Python Script
- Python | Sort Python Dictionaries by Key or Value
- Python | Set 4 (Dictionary, Keywords in Python)
- Python | Add Logging to Python Libraries
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.
