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What are built-in data structures in Python?

Anrutha Dwaram

What are data structures?

Data Structures are used to organize or manage data for efficient access and modification.

Types of data structures in Python

Python has two types of data structures:

  • Built-in Data Structures

  • User-defined Data Structures

Built-in Data Structures in Python

  • list

  • tuple

  • dictionary

  • sets

User-defined data structures

  • Stack

  • Queues

  • Tree

  • Linked List

  • Etc.

Let’s discuss the built-in data structures one by one.

List

  • Lists are mutable, i.e., we can change the value of lists by using certain operations.

  • Lists can store heterogeneous data types.

lst = [1, 2, 3, 4, "a", "b", "c", 38.5, "56.7"]
print(lst)
print(type(lst))
print(type(lst[-1])) 

Append function in list

append() adds an element at the end of the list:

l1 = [1, 2, 3, 4, 5, 6]
l1.append(3)
l1.append([7, 8, 9])
l1.extend([6, 7, 8])
print(l1)

Insert function in a list

insert() inserts an element at the specified element:

l1=[1, 2, 3, 4, 5, 6]
l1.insert(2, 6)
print(l1)

Count function in python

  • count counts the occurrences of a character/number.
l2 = [1, 2, 3, 4, 5, "a", "a", "b", 1, 2, 4]
s = l2.count(4)
print(s)

Sort and sorted function in a list

a = ["b", "g", "a", "d", "f", "c", "h", "e"]
x = sorted(a)
print("a after sorted function")
print(a)
print(x)
b = [1, 2, 5, 8, 3]
b.sort()
print(b)

List Slicing

We use this function to extract certain elements in a list:

lst = [1, 2, 3, 4, 5, 6, 7]
print(lst[0:4])
print(lst[::])
print(lst[::-1])

Deleting elements in the list

There are three functions used to delete elements in a list:

  • pop()
  • remove()
  • clear()
lst = [1, 2, 3, 4, 5, 6, 7]
print(lst.pop())
print(lst)
lst.remove(4)
print(lst) 
lst.clear()
print(lst)

Tuples

A tuple is a collection of objects that are ordered and immutable. Like lists, tuples are sequences. The differences between tuples and lists are:

  • Unlike lists, tuples cannot be changed

  • tuples are represented using () brackets

  • tuples contain heterogeneous values

t = (1, 2, 3, 4, 5, "a", "b", "c")
t1 = 1, 2, 3, 4, "g", "l"
print(t)
print(t1)
print(len(t))

Adding elements in tuple

There is no append function in a tuple, but there is an indirect way of adding elements into the function:

t1 = (1, 2, 3, 4, 5)
t2 = (6, 7, 8, 9)
t3 = t1 + t2 
print(t3)

Max and Min functions in tuple

max(): prints a maximum value in the tuple

min(): prints a minimum value in the tuple

t = (1, 2, 3, 4, 5)
print("Minimum element in the tuple",min(t))
print("Maximum element in the tuple",max(t))

Dictionary

A dictionary is an unordered collection of data values used to store data values like a map. Unlike other data types that hold only a single value as an element, Dictionary holds a key value pair.

dictionary is represented by {}

dict = {1:'a', 2:'b', 5:'c', 4:'d'}
print(dict)
print(dict[5])

Deleting elements in a dictionary

  • pop() deletes certain key in the dictionary
  • popitem() deletes the last element in the dictionary
  • clear() erases all the key-value pairs in the dictionary
cubes = {1: 1, 2: 8, 3: 27, 4: 64, 5: 125}
print(cubes.pop(4))
print(cubes)
print(cubes.popitem())
print(cubes)
cubes.clear()
print(cubes)

Accessing elements in a dictionary

  • key() is used to access the key values in a dictionary
  • values() is used to access the values of dictionary
  • items() is used to access the key-value pair
d = {1:'10', 2:'20', 3:'30', 4:'40', 5:'50'}
l1 =list(d.keys())
print("the key values are:")
print(l1)
l2 = list(d.values())
print("The values are of dictionary is")
print(l2)
l3 = list(d.items())
print("the list items are")
print(l3)

Sets

  • A set is a collection that is unordered and unindexed. Sets are written with curly brackets in Python. Sets do not contain repetitive elements.
  • The Membership operator is used to check if the element is present or not.
  • The remove() function removes certain elements in the set.
set1 = {1, 2, 3, 4, "hi", "world", "python"}
print("python" in set1)
set1.remove(4)
print(set1)
a = {1, 2, 3, 4, 5}
b = {2, 3, 6, 7, 5}
c = a^b 
print(c)
d = a - b
print(d)
e = b - a 
print(e)

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