Function argument basics, membership operators

By now, we have studied certain code blocks. But what if we have a situation where we have codes which needs repetition. We would have to write the same code all over again. For that purpose, we use loops.

But before we start loops, lets learn first a little basics of functions are. We have been using functions all along, right.

print()

range()

list()

set()

dict()

tuple()

were a couple that we used

Lets dive a little deeper into the range() function. functions will have a whole dedicated chapter, so for now, all I want my audience to focus on is, how we use them.

Range() function

You could recall that we used a range() function to generate lists. Actually, range() is just a sequence generator. range() is a python object (which we will cover in depth later)

So, if we make a range(10) and print its output, it'd look something like this.

Its when we create a sequence from it that it generates those numbers.

For now, we will generate numbers using a list function. So, those numbers will be created inside a list.

Depending on the values we pass to the range() function, it generates a sequence of numbers.

For example:

list(range(4))

gives us four numbers, starting from 0:

[0, 1, 2, 3]

Notice that 4 itself is not included.

By default, range() starts at 0 and stops before the number we provide.

We can also tell range() where to start and where to stop:

list(range(2, 6))

gives us:

[2, 3, 4, 5]

We can even specify the step size:

list(range(2, 10, 2))

gives us:

[2, 4, 6, 8]

So, at its simplest, range() can take:

range(start, stop, step)

where:

• start - where the sequence begins
• stop - where the sequence ends (not included)
• step - how much to move forward each time

There are many more things we can do with range(), but these three ideas are enough for now.

As you might have noticed, the end point value is excluded from the range.

$$list(range(2, 5))$$

gives us a range of numbers starting from 2 ending at 4 as the end point is excluded.

These numbers inside range(10, 20) separated by a comma that we enter inside the range functions are called function arguments.

Function Arguments

There could be different types of arguments depending on how a particular function works. We'll have a whole dedicated section on function arguments later. For now, let's focus on the range function and its arguments.

Notice the third argument that is the step argument

Lets increase the step counter and use a different range of numbers

print() function

We have been using the print function since the first class. Now, lets use the knowledge of function arguments to understand this print function.

The "Hello, world" string we passed inside the print function, was print function's first argument.

print by default will print any values we pass inside it. Lets print multiple values now.

We can print all of these 4 variables with just one print function

We could get creative here and print whatever we want

String Formatting

We will later learn, how to print these things in a better fashion using string formatting.

But just as an example for our beautiful curious audience, let me show how print function could be used with string formatting

Note: I'll say again, we will cover string formatting much later in the ebook.

Remember Multi-line strings?

It's okay, multi-line strings are just strings written over multiple line. Let's use them

Membership Operators

Remember, we left the membership operators for later.

There are two membership operators in python.

They are used to check if a value exists inside a sequence.

The in keyword

Python says, yes the value 1 exists inside the list of elements [1, 2, 3]

Python says the value 12 does not exist inside the list.

The not in operator

Just the opposite of in operator, because we used not keyword here to reverse the output