While loop still looping

Question

I need to have 'F' or 'M' as input from the user. So there is my code :

a = input("")
while a != 'F' or a != 'M':
    a = input("")

But it still looping even if the user enter 'M' or 'F' or anything else. so I've tried this :

genre = input("")
while genre != 'F':
    genre = input("")

And it works.. I just need to have 'M' OR 'F', could someone help me with this?

Thank's in advance

Your condition is **always true**, it doesn't matter what the value of `a` is. *At least one* of your two `!=` conditions will be true (`a` can't be set to `F` and `M` at the same time), and `or` on `True or False` or `False or True` or `True or True` will always be true. You want to use `and`, you want both tests to be true *together, at the same time*. — Martijn Pieters, Dec 09 '18 at 11:44

hiro protagonist · Answer 1 · 2018-12-09T11:33:54.497

1

one of a != 'F' or a != 'M' will always be True. try this:

while a not in 'FM':
    ...

although this will also accept FM; the better way is to use:

while a not in set('FM'):
    ...

edited Dec 09 '18 at 11:33

answered Dec 09 '18 at 11:18

hiro protagonist

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File "", line 2 while a not in 'FM' ^ SyntaxError: invalid syntax – Fatih Akman Dec 09 '18 at 11:20
that is not enough information to help. what *exacly* caused the syntax error? what are the lines before and after the `while`? is the indentation correct? – hiro protagonist Dec 09 '18 at 11:23
i've tried this in the console – Fatih Akman Dec 09 '18 at 11:31
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@FatihAkman: You missed the `:` at the end. – Graipher Dec 09 '18 at 11:33

score 1 · Accepted Answer · answered Dec 09 '18 at 11:24

1

You need and instead of or

while a != 'F' and a != 'M'

because a can't be equal to two things at a time. As it is now, if a=='M', then a != 'F', so the loop continues (the same for the reverse values). So, the loop will never end.

answered Dec 09 '18 at 11:24

blue_note

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thank's a lot , but i've now this problem : – Fatih Akman Dec 09 '18 at 11:43
danger = input("") while type(danger) != int: danger = input("") it still looping whatever i put the input – Fatih Akman Dec 09 '18 at 11:43
what you get from `input` is always a string. so you need to convert it to `int`. – blue_note Dec 09 '18 at 11:47
like this ? : danger = int(input("") but if i enter a string i will have an error because not the right type and i need to accept this error of wrong type without except. I need to loop while i have not an int – Fatih Akman Dec 09 '18 at 11:52
you can't do that in `while` alone. you can to use `try/except` to convert it to integer – blue_note Dec 09 '18 at 12:45

While loop still looping

2 Answers2