while loop add numbers!

[glao]

Hello ,

I can't understand why this loop doesn't work as I wanted.
Why the continue statement isn't executed.
I want the code to count only the user input which is 1 or 2 and stop when the sum is >=25.

i = 0
user = input('Enter '1' or '2': ')

while True:
    if ( user == '1' or user == '2' ):
        i += int(user)
        print('Sum is {0}'.format(i))
        if i < 25:
            continue
        else:
            break

    else:
        print('Invalid input')
        user = input('Enter '1' or '2': ')

Right know if I run the program it gives:

Enter '1' or '2': 1
Sum is 1
Sum is 2
Sum is 3
Sum is 4
.....
Sum is 25

[Gribouillis]

Write pseudo code to show the logic of your code. I suggest

while True:
    get user input
    if input is invalid:
        print error message
        continue
    process user input (update sum)
    if exit condition is met:
        break

[glao]

Hello ,

1) The 'get user input' , I think it's ok if I have it initially outside the loop,yes?

2) Doing something like:

i = 0

while True:
    user = input('Enter '1' or '2': ')

    if ( user == '1' or user == '2' ):
        i += int(user)
        print('Sum is {0}'.format(i))

    else:
        print('Invalid input')
        user = input('Enter '1' or '2': ')
        continue

    if i >= 25:
         break

results in working generally ok , but when I enter:

Sum is 0
Enter '1' or '2':1
Sum is 1
Enter '1' or '2': 2
Sum is 3
Enter '1' or '2':2
Sum is 5
Enter '1' or '2': 1
Sum is 6
Enter '1' or '2': 4
Invalid input
Enter '1' or '2': 1
Enter '1' or '2':1
Sum is 7

It misses a count after the 'invalid input'.
I can't figure!

Thank you!

[glao]

Hmm..

I changed to :

i = 0
while True:
    user = input('Enter '1' or '2': ')
    if ( user != '1' and user != '2' ):
        print('Invalid input')
        continue
    else:
        i += int(user)
        print('Sum is {0}'.format(i))

    if i >= 25:
         break

and it works!

But ,I can't figure why??

Previously I had :

   if ( user == '1' or user == '2' ):
        i += int(user)

Now:

if ( user != '1' and user != '2' ):
            print('Invalid input')
            continue

But , isn't it the same??

[rproffitt]

Read http://programmers.stackexchange.com/questions/201175/should-i-use-parentheses-in-logical-statements-even-where-not-necessary falls pretty much in-line with how I think and code. Without the parentheses you must know how your language works.

There are purists that can go either way. I want it clear in the code what I wanted to say.

[Gribouillis]

@glao you are not posting your actual code: 'Enter '1' or '2': ' is not a valid python string. Use copy and paste to write your code.
Your previous version failed because there was an extra user = input(...) in the invalid input part.
rproffitt's suggestion is not a bad thing, but it's not the issue here.
The rules of operator precedence for python are here.

[glao]

Yes , it is

 input('Enter 1 or 2: ')

Only this was wrong.But I can't understand why it misses a count after an invalid input when I use

if ( user == '1' or user == '2' ):



Your previous version failed because there was an extra user = input(...) in the invalid input part.


Ok for this,thanks

Thank you!

[Gribouillis]

But I can't understand why it misses a count after an invalid input when I use

It doesn't have anything to do with the if test. Look at your code and you will see that there are two lines user = input(...) instead of one.

[glao]

Oh yes!You are right!
Thank you very much for your help!