‫So up until now, we learned that strings can be accessed quite easily.
‫And using the square brackets, we can access different parts of the string.
‫And this idea of a start, a stop and a step over is what we call slicing or string slicing, because
‫we can slice the string however we like.
‫But we also need to learn another important term that's going to come up again and again throughout
‫this course.
‫And as a matter of fact, it's an important concept that as you get more advanced into programming,
‫you really need to understand what is this concept?
‫Well, it's this idea of immutability.
‫It's an important term in programming.
‫What does immutability mean?
‫Well, strings and python are immutable.
‫That means they cannot be changed.
‫What I mean by that.
‫Now that we've assigned selfish this value, this string.
‫Well, I can reassign it, right?
‫I can say selfish is 100 now.
‫And if I print selfish.
‫And I click run.
‫That works.
‫But if I instead do something like the first index of selfish is going to equal eight and I click run.
‫I get an error, I get a typo error saying string object does not support item assignment.
‫Why is that?
‫Because strings are immutable.
‫That is, I cannot change the value of this once it's created.
‫I can just immediately change it to eight.
‫One, two, three, four, five, six, seven.
‫No, it has to stay the same.
‫The only way that I can remove this or change this is to completely reassign the value.
‫So that in memory Python removes all of this from our bookshelf of memory and instead just assigns eight
‫into the zero bookshelf and removes everything else because we don't use it anymore.
‫Now this idea of immutability is something we'll explore more and more, especially when we start talking
‫about lists.
‫But for now, just remember that you can't reassign part of a string.
‫Once created, it exists like that in that form.
‫The only way we can change it is to create something new.
‫We can do selfish plus eight and we can create it that way.
‫But now this selfish is a whole new string.
‫This no longer exists, and a whole new shelf space was created for us to use this whole new string.
‫Again, if this doesn't make sense to you or why it's important just yet.
‫Don't worry.
‫We'll get there.
‫For now, though, I'll see you in the next video.
‫Bye bye.