Pointers


We saw that behind the scenes, Arrays don't store raw data inside of them - instead, they store pointers to their data.
It turns out that \i{every} data structure stores pointers to their data. Everything's made up of pointers! Even variables are pointers in Python!

The amazing result of this is that whenever you write `A = B`, Python points `A` to `B`. There are no exceptions.
Here's an example where we run one line of code at a time, and we show you the picture you should have in mind as the code runs. 

``
# point x to 99:
x = 99
``

\image{0, 100}


``

# point x to 100:
x = 100 

``


\image{.5, 100}

``
# point x to the array:
x = [1,2,3] 
``
\image{1, 160}
``
# point y to x:
y = x 
``
\image{2, 160}

``
# point x[1] to 9:
x[1] = 9 
``
\image{3, 160}



Note that as the code ran, we changed y, but x changed too! This is confusing behavior to beginners, but it's easy to understand once you know everything's made of pointers in Python, and `A = B` \i{always} points `A` to `B`. 




Data Structures

Pointers