Denis - 7 months ago 33

Python Question

For the first time wrote "Do you want rety ? (y or n)" I always get an this output "wrong ! try again .". After that its working good but it first time gives error.

`def factorial(n):`

r=1

if n==0:

return

else:

for i in range(2,n+1):

r=r*i

return r

n=int(input("Give a number : "))

b=factorial(n)

print (n,"!", "= ",b)

a=str(input("Do you want rety ? (y or n) \n"))

while (a != "y" or a != "n" or a!="Y" or a!="N"):

print("wrong ! try again .")

a=str(input("Do you want rety ? (y or n) \n"))

if a=="y" or a=="n" or a=="Y" or a=="N":

break

while a=="y" or a=="Y":

n=int(input("Give a number : "))

b=factorial(n)

print (n,"!", "= ",b)

a=str(input("Do you want rety ? (y or n) \n"))

if (a=="n" or a=="N"):

print("thanks for using")

Answer

Change your condition in first while loop from `a != "y" or a != "n" or a!="Y" or a!="N"`

to

```
while a not in ['y', 'Y', 'n', 'N']
```

*Explanation:*

Let say `a = "Y"`

, then `a`

won't be equal to `"n"`

. Hence your condition with `or`

will always be `True`

.

If you are interested in `or`

logic, write it as (but `not in list`

is cleaner):

```
while not (a == "y" or a == "n" or a=="Y" or a=="N")
```

Source (Stackoverflow)