assert

• assert

 If a condition in your code returns True, if not, the program will raise an AssertionError.

 

def cal(nums):
    assert len(nums)>0, "list must not be empty"
    total=sum(nums)
    avg=total/len(nums)
    return avg

data=[5, 10, 15, 20]
result=cal(data)
result
>>>

12.5

 

You can write a message to be written if the code returns False.

def cal(nums):
    assert len(nums)>0, "list must not be empty"
    total=sum(nums)
    avg=total/len(nums)
    return avg

data=[]
result=cal(data)
result
>>>

AssertionError                            Traceback (most recent call last)
/var/folders/x2/28kczyld7b702fsq79qmmgcm0000gn/T/ipykernel_33502/3200075429.py in <module>
      6 
      7 data=[]
----> 8 result=cal(data)
      9 result

/var/folders/x2/28kczyld7b702fsq79qmmgcm0000gn/T/ipykernel_33502/3200075429.py in cal(nums)
      1 def cal(nums):
----> 2     assert len(nums)>0, "list must not be empty"
      3     total=sum(nums)
      4     avg=total/len(nums)
      5     return avg

AssertionError: list must not be empty

https://www.browserstack.com/guide/assert-in-python#:~:text=Assert%20in%20Python-,What%20is%20Assert%20in%20Python%3F,the%20execution%20of%20a%20program.