In this section we will cover first Python Data Structure - List or what in other programming languages is called an array.

Lists can contain no values whatsoever, be empty, or as many objects as RAM allows us to hold. What is more, it so happens that in Python lists can hold any types of values, it could be other objects, functions, strings, integers, your own data types or even other lists. What is also important to mention is that we can change values within the list, lists are mutable python objects.

The notation of the list is simply these brackets: [ ] two brackets with values in between separated by commas.

my_list = [] # Instantiating empty list

There is method called .append() that allows to insert an item into the list: append(<object>)

my_list = []

name = "Tom"
my_list.append(name)
print(my_list)

Since there can be dublicated values within the list this function allows us to calculate the frequency of the item within the list

my_list = [1, 1, 2 ,3 ,4 ,5]
print(my_list.count(1)) # 2

As we have seen append always adds the value to the end of the list, .insert() allows us to add the value to which ever index we want:

my_list = [1, 1, 2 ,3 ,4 ,5]
my_list.insert(1, 50)
print(my_list) # [1, 50, 1, 2, 3, 4, 5]

Name speaks for itself. With this method we will simply drop a particular value from the list:

my_list = [1, 1, 2 ,3 ,4 ,5]
my_list.remove(1)
print(my_list)

The function will remove the first occurence of the object found. If you want to remove particular item from the list, you can do that with slicing mechanism:

my_list = [1, 1, 2 ,3 ,4 ,5]
my_list.remove(my_list[-1]) # removing last item from the list
print(my_list) [1, 1, 2, 3, 4]

As we have already seen such functions as print and probably a few others along the way, Python lists also make use of quite a few of them so we do not have to reinvent the wheel each and every time.

Note that we do not have the "." symbol now, meaning that there are standalone functions that do not belong to a particular data type.

As we have previously discussed lists can be of whatever length, so it would be nice to know how big of a list we are dealing with. len() comes in handy here:

my_list = ["name", 123, None, True]
print(len(my_list)) # 4

If you have list of int, float values you may find out maximum value with this function:

my_list = [50, 99, 1, -50]
print(max(my_list))

If you have list of int, float type values you may find out minimum value with this function:

my_list = [50, 99, 1, -50]
print(min(my_list))

The biggest strength within the lists is that we can have a list of certain actions, objects that we want to do one after another, we can iterate over them and do some actions.

my_list = [1, 2, 3]
for item in my_list:
    print(item)

or we could do some operations along the way as well!

my_list = [1, 2, 3]
for item in my_list:
    print(item + 20)

my_list = [1, 2, 3]
my_list[2] = 5
print(my_list)

As with the string we can also be slicing items withing the list as well. Each and every item in the list contains an index starting at 0. So we can perform same type of slicing:

my_list = ["first", "second", "third"]
print(my_list[-1])
print(my_list[:1])
print(my_list[::2])
print(my_list[::-1])
print(my_list[0:2])

If you want to check if a certain object is in the list you may do something like this:

my_list = [1, 2, 3]
print(1 in my_list)

Another very similar python built-in data structure is Tuple. The main difference here is that Tuple is immutable. Meaning that we have an object that contains multiple values, they can be duplicated, almost all characteristics are similar except that the items in Tuple by design cannot be changed.

Tuple notation in python is ( ) - two parentheses with values in between separated by commas.

empty_tuple = ()
tuple_single_item = (1,)
another_tuple = (1, 2, 3)

Note that single item tuple must contain comma, even though it's just a single item. Other than that it is all the same as the List

Those are simply exactly the same, except that you are unable to mutate the tuple. If you try doing so, you will get an error:

🛑

my_tuple = (1, 2, 3)
my_tuple[0] = 500 # TypeError: 'tuple' object does not support item assignment

Now it seems that Lists are much better than tuples, but in programming everything is not always one sided and it depends on certain situations. Usually it is recommended to use Tuple on static values that do not change as it is a bit faster in python than lists. And we should be using lists whenever we have values that are going to be changing, or the list itself will grow or shrink in size.

All answers must be printed in terminal

1. Write a python program that sums up all items in the list (all items are integers or floats in list, create a list yourself).
2. Write a python program that multiplies all items in the list (all items are integers or floats in list, create a list yourself).
3. Write a python program that gets maximum value from the list (all items are integers or floats in list, create a list yourself).
4. Write a python program that concatenates all strings in the list (all items are strings, create a list yourself).
5. Create two lists and add them together, make sure it works the way you want it to.
6. Write a python program that asks user to enter 3 integers and find the highest value entered.
7. Try doing same exercises with tuples.

• w3schools
• more material