Why does nums.index(10) show a ValueError: 10 is not in list?

# this does not really create a list
nums = range(1, 10, 2)
# if you print nums
# you will get
range(1, 10, 2)

# if you want to get a list from range(1, 10, 2), you will need to wrap this in a list(), like so
nums = list(range(1, 10, 2))
# ^ this will now return this when you try to print nums:
[1, 3, 5, 7, 9]
# ^ this makes sense, since range says to start at 1, skip every 2, until 10
# so all odd numbers from 1 - 10, which are 1, 3, 5, 7, 9

# Now, the reason why you where getting 2 when you typed:
nums.index(5)
# is because if you look at the list, [1, 3, 5, 7, 9]
# the number 5 is in the 2 index of that list
# so what .index(X) does, it look at the list for whatever number is passed in
# and it returns the index where that number is located

# The reason why you were getting ValueError when you typed:
nums.index(10)
# is because 10 is not in the list [1, 3, 5, 7, 9]
# if you did
nums.index(1) # you would get 0
nums.index(3) # you would get 1
nums.index(5) # you would get 2
nums.index(7) # you would get 3
nums.index(9) # you would get 4


# hope that helps