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Start your free trial###### ben127127

1,980 Points# I am confused about the raise function

What exactly is the "raise" function doing?

I don't understand why we have to move the line: amount_due = split_check(total_due, number_of_people) within the try block. If we enter zero, for example, shouldn't that "raise" the exception ValueError, thus prompting the except to print "Oh no!...etc" and make that line irrelevant?

## 2 Answers

###### boi

14,241 Points"the else: block should only run if the try: block does not prompt the except: block. So, the else block should only run if there is no ValueError"

Yes, Correct

"However, before moving the referenced line of code within the try block, number_of_people should register as less than or equal to 1, prompting ValueError to be raised, and therefore running the except: block and not the else: block. So it should never deliver the traceback message because the line "amount_due = split_check(total_due, number_of_people)" should never run. Help me understand where I'm going wrong"

Ok, let me first declare the referenced line;

```
amount_due = split_check(total_due, number_of_people) #This is the referenced line
```

Alright, say the referenced line is in the else block, and now you run the code.

Running the code ;

```
import math #First line of code, the program will import math module
def split_check(total, number_of_people):# This is a function, and the program does NOT execute the function if
# there is NO call, so it will move forward to the next line of code and
if number_of_people <=1: # when this function is called, it will come back here and run this function
raise ValueError("More than 1 person is required to split the check")
return math.ceil(total / number_of_people)
```

Read the comments carefully, Now the program will go to the next step ( Python executes code in sequence).

next step;

```
try:
total_due = float(input("What is the total? ")) # Here the program will prompt you for an input, say u give it 100
# the input 100 will be stored in the variable total_due
number_of_people = int(input("How many people? ")) # Here the program will prompt you for input again, say you
# give it 0 or 1, the input will be stored in number_of_people
# NOTHING actually happened in the Try block but only values have been stored, so the program moves to the next step
# and the except block is SKIPPED entirely
except ValueError as err: #SKIPPED
print("Oh no! That's not a valid value. Try again...")
print(err)
else: # After the try block the program comes to the else block because the except block never ran or executed.
amount_due = split_check(total_due, number_of_people) # NOW a function is called here, so the program goes to the
# function block, which is at the top.
print("Each person owes ${}".format(amount_due))
```

Now the program will go through the function block which is the amount_due = split_check(total_due,number_of_people)

now going through the function below;

```
def split_check(total, number_of_people):
if number_of_people <=1: # The program checks what value does "number_of_people" have.
#we gave the number_of_people a value of 1 or 0, since the condition is TRUE the program executes the IF block.
raise ValueError("More than 1 person is required to split the check") #Here it finds the "raise ValueError".
# Since the "raise ValueError" executed the program ENDS and gives a traceback with the following message,
# ValueError : "More than 1 person is required to split the check"
return math.ceil(total / number_of_people)
```

The End

I hope this gave you some clarification.

###### boi

14,241 PointsHey Ben!

let's break it down slowly. Below is the Craig code

```
import math
def split_check(total, number_of_people):
if number_of_people <=1: # A condition is set here, and if the condition is "True", A ValueError will be raised.
raise ValueError("More than 1 person is required to split the check")
#if the above condition is "False" the below code will execute.
return math.ceil(total / number_of_people)
```

In simple words, the "raise" function will give out a ValueError with the message " More than 1 person is required to split the check" if the number of people is less than or equal to 1.

Now for the second part of your question.

```
import math
def split_check(total, number_of_people):
if number_of_people <=1:
raise ValueError("More than 1 person is required to split the check")
return math.ceil(total / number_of_people)
try:
total_due = float(input("What is the total? "))
number_of_people = int(input("How many people? "))
amount_due = split_check(total_due, number_of_people)
except ValueError as err:
print("Oh no! That's not a valid value. Try again...")
print(err)
else:
print("Each person owes ${}".format(amount_due))
```

The reason that this line: amount_due = split_check(total_due, number_of_people) is moved within the try block is to handle the error properly.

If the line: amount_due = split_check(total_due, number_of_people) is not placed in the try block it would "raise" an error but with all the Traceback nonsense.

for example:

```
import math
def split_check(total, number_of_people):
if number_of_people <=1:
raise ValueError("More than 1 person is required to split the check")
return math.ceil(total / number_of_people)
try:
total_due = float(input("What is the total? "))
number_of_people = int(input("How many people? "))
# removed the line from here
except ValueError:
print("Oh no! That's not a valid value. Try again...")
else:
amount_due = split_check(total_due, number_of_people)
print("Each person owes ${}".format(amount_due)) #placed the line here
# In the python shell, running the code!!!
what is the total? #input 100
how many people? #input 0
#output
Traceback (most recent call)
File "Check_please"Traceback (most recent call last):
File "check_please.py", line 18, in <module>
amount_due = split_check(total_due, number_of_people)
File "check_please.py", line 6, in split_check
raise ValueError("More than 1 person is required to split the check")
ValueError: More than 1 person is required to split the check
```

Do you see all that Traceback nonsense, to avoid this you put the line: amount_due = split_check(total_due, number_of_people) into the try block so that the error can be handled properly

```
import math
def split_check(total, number_of_people):
if number_of_people <=1:
raise ValueError("More than 1 person is required to split the check")
return math.ceil(total / number_of_people)
try:
total_due = float(input("What is the total? "))
number_of_people = int(input("How many people? "))
amount_due = split_check(total_due, number_of_people)
except ValueError as err:
print("Oh no! That's not a valid value. Try again...")
print(err)
else:
print("Each person owes ${}".format(amount_due))
# In the python shell, running the code!!!
what is the total? #input 100
how many people? #input 0
#output
Oh no! That's not a valid value. Try again...
More than 1 person is required to split the check
```

See the error messages are showing without that traceback nonsense

I hope you got at least some idea.

###### ben127127

1,980 PointsHi. Thanks so much for the in-depth response. I'm still a little confused though - so, from my understanding, the else: block should only run if the try: block does not prompt the except: block. So, the else block should only run if there is no ValueError. However, before moving the referenced line of code within the try block, number_of_people should register as less than or equal to 1, prompting ValueError to be raised, and therefore running the except: block and not the else: block. So it should never deliver the traceback message because the line "amount_due = split_check(total_due, number_of_people)" should never run. Help me understand where I'm going wrong

## ben127127

1,980 Points## ben127127

1,980 PointsThank you so much! I understand now.

## boi

14,241 Points## boi

14,241 PointsGlad it helped, you could mark the answer as "Best Answer" to help others be aware that the question has been answered.