all right, so lesson number one fundamentals. What is Python? Python is a programming language. What that means is it's a human-readable language that can communicate with a computer. This means that we can write stuff in it that we understand, and the computer also understands. Now, this is an IPython interpreter, as I've explained before, so I can type out lines of code, and we can see what would happen if we execute them. Now, because computers mainly think in numbers, we can talk to the computer in numbers at its most fundamental level. So, we can do some arithmetic. Three multiplied by three gives us nine. We could do three plus five to give eight or eight divided by six to give us one and a third. Now, we can keep doing this. We can keep doing all kinds of calculations and use it as a calculator, but at some point, we're going to get to a level where we need to store a variable because we want to use it for later, and we don't want to type it out. A good example might be the square root of 2.

which is going to be 2 to the power of minus well to the power of 0.5, which is 1.414, etc. Now writing that out every time is quite a pain, so instead we can assign it to a variable, and to assign it we need to use the assignment operator, which is an equals sign. What this does is we say, Okay, this value I'm going to work out what it is, and then I want to assign it to, and then we create a variable. Let's call it x, right? So what we've done is we created a brand new variable called x, assigned the value of the square root of 2 to it, and now we can use x in place of the square root of 2 for the rest of the program's lifespan. So x is now equal to this. We can multiply x by something else, we can divide x by something else, we can just continue to use x however we wish. In fact, we can then use it in another calculation, which we assign to another variable. Let's call them y.

y is now equal to 0.2357, whereas x is still equal to the square root of 2. And this is a very powerful tool. Now, when we use these assignment operators, it doesn't really care whether or not the variable exists yet. As you saw, if it doesn't exist, it's created. Well, what happens if it does exist? Well, if I was to say, assign x to be equal to 2 to the power of, let's say, 0.3 instead of a half, that is going to just overwrite the previous value. So, this is how we edit variables. All we really need to do is perform another assignment, and it's overwritten. It's very powerful. So, so far, we've seen two types which you may not be initially aware of, but essentially, we have singular natural numbers. These are the integers, and we have these decimal point values like x at the moment, which is a floating point value. We can actually look at these types by using the type function. We can type type of x, and that's a float type. We could do

type of 2 that's an integer type int. Now there's a third type that I want to talk about before we move on, which is the string. Strings are denoted by quotes, pairs of them in fact. String strings can be pairs of single quotes or pairs of double quotes. They are equivalent, but they cannot be a single quote and a double quote; that is a syntax error. Strings can be assigned to variables, much like numbers can, and they're collections of these alphanumeric characters, although technically they can be any Unicode character. Now that we have our string, and we have a float, and an integer, we can then do other things. One of which, which we will need to talk about, is the print statement. This is quite a fundamental one that will come up a lot throughout this course. You won't see me using it very much in the IPython interpreter because of this returning to screen aspect. It's not particularly necessary, but as soon as you're writing code in a full Python script or in the Jupyter notebooks, you might want to use it a bit.

more basically, it takes a variable or set of variables separated by commas and then prints them to the screen separated by spaces like so. Now, in addition to this, you may wish to look at, you may wish to write something alongside your print statement to explain why you're doing, or maybe your expression, maybe your calculation. You might want to say x is the value of density in this case, so we could do s is equal to 2 to the power of 0.5. Now, we can add a comment. A comment is anything that comes after this hash symbol, so we type hash, and then we can write anything we want, and the Python interpreter will just ignore that. That's a comment. We can write one here, and that's also ignored. It's a blank statement. You might be wondering what's the point with this, but you'll see it can be quite useful, and I use them throughout the course, which is why we mention them now. All right, that brings me to the end of lesson one. We've looked at how it can be used a

Python can be used as a calculator. We've done some basic variables assignment editing usage. We've had a look at the different types, and we've also looked at print and comments. The only thing left to mention is how variable names work. So far, I've been using x, y, and z, but you can use any sort of alphanumeric combination to do so. In fact, variables can be any of the 26 letters or any combination thereof, as well as using numbers and the underscore character. So, this is a variable 9 is equal to 5. This is a variable 9 is now a variable. There is one useful aspect of this to remember, though, which is that they are case-sensitive. So, this is a variable 9, but with a capital T, it will be different from the one with the lowercase one. So, now you can see this is a variable nine, and this variable nine are different. You also cannot start a variable with an integer or a number. So, this is a variable will be a syntax error because you cannot start a variable name with a

number there you go, and with that, we've covered everything you

Fundamentals of Python — Lesson 1

Fundamentals of Python — Lesson 1