Question

I was just playing in IDLE and wrote the following:
>>> sum = 0.0
>>> for i in range(10):
sum = sum + 0.1
frustratingly it was giving me traceback errors saying in line 2, + is not a valid action or so. then i reopened the IDLE and wrote the same program. Sure enough it was working just fine this time as it should be. Any idea why the error was happening the first time around?

Answer 1

Hmmm.... Did you perhaps type sum = "0.0" the first time?

Answer 2

hey thanks! yes i did write that the firt time..and the second time too..

Answer 3

Becaus if you use quotes, that makes it text, not a number.

Answer 4

ok u mean with the quotations..no i dont think so..let me check

Answer 5

sum is a built-in operation, that should be a problem

Answer 6

See, like this:
```
>>> sum = "0.0"
>>> for i in range(10):
sum = sum + 0.1



Traceback (most recent call last):
File "<pyshell#3>", line 2, in <module>
sum = sum + 0.1
TypeError: cannot concatenate 'str' and 'float' objects
>>> sum = 0.0
>>> for i in range(10):
sum = sum + 0.1


>>> print sum
1.0
>>>
```

Answer 7

no i didnt use quotations..:(

Answer 8

@Turing test, if it was how come it worked later?

Answer 9

Turing, it is a function, not an operation, but yes, always best to avoid those.

Answer 10

no it works, i checked. my mistake

Answer 11

it's not an indentation issue?

Answer 12

no i dont think so...i should have copied the traceback error though...to make things clearer..

Answer 13

Yah, without the traceback it is hard to say. Perhaps a small typo. Then it would be undefined.

Answer 14

For example:
```
>>> ================================ RESTART ================================
>>> sim = 0.2
>>> for i in range(10):
sum = sum + 0.1



Traceback (most recent call last):
File "<pyshell#12>", line 2, in <module>
sum = sum + 0.1
TypeError: unsupported operand type(s) for +: 'builtin_function_or_method' and 'float'
```

Which is why it is best to use var names that are not function names.

Answer 15

yeah perhaps so..thing is it is so silly it was driving me mad..also more later when the code actually worked..anyways..perhaps it was nothing...thanks a lot u both..really appreciate it..:)

Answer 16

np. Have fun!

Answer 17

or sometimes just restarting IDLE fixes it, too :P

Answer 18

" unsupported operand type(s) for +"! YES! that's what it told me!

Answer 19

haa...haa...u got that right @Turing! :D

Answer 20

:)

Answer 21

Yah, if it said unsuppored operand it was some sort of type mismatch, which a typo can do. And like Turing pointed out, it is just best to avoid the built-ins as var names. These are them:
https://docs.python.org/2/library/functions.html

Answer 22

thanks @e.mccormick! i'll watch out next time! :)