Decrease value of "i" in Python

Question

When num is not between 10-20 , I need to decrease i value in else part. How can I do that?

Here is my code:

arr = []

for i in range(10,20):
    num = int(input("Enter Number: "))
    if num > 10 and num <= 20:
        arr.append(num)
    else:
        i = i - 1
print(arr)

Answer 1

Your loop cycles over a range of int numbers. Reducing the int i at the end of the loop does not help, since in the next loop cycle the next instance out of the range is taken as i .

You could solve this in different ways. One is mentioned by @Tomerikoo in the comments.

If you want to keep the loop construct similar to what you tried, you can do this:

arr = []
i = 0
while i < 10:
    num = int(input("Enter Number: "))
    i += 1
    if num > 10 and num <= 20:
        arr.append(num)
    else:
        i = i - 1
print(arr)

But you could also do without i:

arr = []
while len(arr)<10:
    num = int(input("Enter Number: "))
    if num > 10 and num <= 20:
        arr.append(num)
print(arr)

note that the programs do not gracefully react if non-integers are entered