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Python Python Basics (2015) Logic in Python Try and Except

Jason Portilla
Jason Portilla
15,345 Points
Posted by Jason Portilla
Jason Portilla
15,345 Points

I don't understand what i'm doing wrong in the 3 part of the challenge with exceptions

You're doing great! Just one more task but it's a bigger one.

Right now, we turn everything into a float. That's great so long as we're getting numbers or numbers as a string. We should handle cases where we get a non-number, though.

Add a try block before where you turn your arguments into floats.

Then add an except to catch the possible ValueError. Inside the except block, return None.

If you're following the structure from the videos, add an else: for your final return of the added floats.

trial.py 
def add(num1, num2):
    try:
        return float(num1) + float(num2)
    except ValueError:
        return none
    else:
        print(num1 + num2)
Boris Aroche
.a{fill-rule:evenodd;}techdegree
Boris Aroche
iOS Development Techdegree Student 555 Points

Did you figure this one out? I'm still really confused about challenge 3

Jason Portilla
Jason Portilla
15,345 Points
Jason Portilla
Jason Portilla
15,345 Points

Boris what I understand is under the try: block, it converts num1 and num2 into a float. If it a number then it passes and skips the except block and go to the else block. In the else block it prints out the float of num1 + num2. The Except block happens when something other than a number is entered inside the arguments. This returns None which is nothing and the program ends.

Gary Gibson
Gary Gibson
5,011 Points
Gary Gibson
Gary Gibson
5,011 Points

I think the else should be followed by return(float(num1) + float(num2)), not print(num1 + num2). That's the structure that worked for me. The code asked for "return", not "print." And you have to be sure your arguments are still converted to floats in this part of the block

else:

return(float(num1) + float(num2))
Justin Burnett
Justin Burnett
3,427 Points

This one through me for a loop, and even with looking at the answers i'm not sure i'm following the logic.... I think i need to redo this whole course now =\

7 Answers

Kevin Faust
Kevin Faust
15,353 Points
Kevin Faust
Kevin Faust
15,353 Points

just gotta capitalize the n in none at line 5. should be None

Patric Daniel Pförtner
Patric Daniel Pförtner
1,542 Points
Patric Daniel Pförtner
Patric Daniel Pförtner
1,542 Points

Hi Jason,

You are very close to the answer, here is how I did it: 

def add(num1, num2):
    try:
        return float(num1) + float(num2)
    except ValueError:
        return None
    else:
        print(num1 + num2)

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Mathew V L
Mathew V L
2,910 Points

Why is the else print?

The exercise says for your final return which is confusing

vijaya inturi
vijaya inturi
538 Points
vijaya inturi
vijaya inturi
538 Points

def add(x, y): try: return float(x) + float(y) except ValueError: return None else: print(x+ y)

nathanielcusano
nathanielcusano
9,808 Points
nathanielcusano
nathanielcusano
9,808 Points 
def add(a, b):
    try:
        C=  float(a) + float(b)
    except ValueError:
        return None
    else:
        return C 

add("123", 2)
# Basically you need to store the sum in variable C. However, if you call the function
# with something like "zq23" it won't recognize it either as a string nor as an integer and
# will not be able to convert it to a float ,so you will get the value error.
# You could also choose to store float(a) and float(b) in a separate variable like D = float(b) 
# In that case, you would want to return C + D
# I called it with "123" and 2 so it gets converted to 123 and the sum is 125. You can check 
# this at pythontutor.com to see more clearly
mckbas
mckbas
14,166 Points
mckbas
mckbas
14,166 Points

This is what worked for me:

def add(x, y):
try:
return float(x) + float(y)
except ValueError:
return None
else:
return x + y
sai jayanth kashyap
sai jayanth kashyap
3,293 Points
sai jayanth kashyap
sai jayanth kashyap
3,293 Points

its not working for me. ''' def add(x, y): try: return float(x) + float(y) except ValueError: return None else: return x + y '''

ali mur
seal-mask
.a{fill-rule:evenodd;}techdegree
ali mur
UX Design Techdegree Student 23,377 Points
ali mur
.a{fill-rule:evenodd;}techdegree
ali mur
UX Design Techdegree Student 23,377 Points

you need to indent your code.

daniel escobar
PLUS
daniel escobar
Courses Plus Student 563 Points
daniel escobar
daniel escobar
Courses Plus Student 563 Points

For those who get errors, I highly recommend that you try your code in workspaces because it tells you where your error is. For me, it took me a long time until i figure it out that my issue was indentation. Trust me, try your code in workspaces