Help me by explaining this code.

Question

nums = [(X,X**2) for X in range (1,5)]
print (nums [2] [1])

The output is 9
I don't really understand how the output is 9, so if someone could help me by offering a step-by-step explanation that would be great!

Answer 1

nums is attributed a so-called "list comprehension", a special statement for creating lists or other collections.
It tells Python to create a list of tuples (x, x**2) where x takes values of 1 to 4. So it goes: [(1, 1**2), (2, 2**2), (3, 3**2), (4, 4**2)] which of course equals to [(1, 1), (2, 4), (3, 9), (4, 16)]

Then you call the list's element number [2] - (3, 9) - and access the tuple's element number [1] - equal to 9.

Answer 2

Didn't know what tuples were yet, so that caused some confusion, but I get it now. Thanks!