Printing an int list in a single line python3

You want to say

for i in array:
    print(i, end=" ")

The syntax i in array iterates over each member of the list. So, array[i] was trying to access array[1], array[2], and array[3], but the last of these is out of bounds (array has indices 0, 1, and 2).

You can get the same effect with print(" ".join(map(str,array))).

Yes that is possible in Python 3, just use * before the variable like:

print(*list)

This will print the list separated by spaces.

(where * is the unpacking operator that turns a list into positional arguments, print(*[1,2,3]) is the same as print(1,2,3), see also What does the star operator mean, in a function call?)