Online Training
Q4 2024

Nov 19 to Dec 10

11.00 AM EST: USA, UK, Canada, Mexico and Europe

06.00 AM GMT: MiddleEast, Asia and Australia

Register Now
Topics
  1. Lists
  2. Loops

Lists

Introduction to Lists

In Python, lists are ordered collections of items that allow for easy use of a set of data. 

                                

primes = [2, 3, 5, 7, 11]
print(primes)
empty_list = []
Adding Lists Together

List values are placed in between square brackets [ ], separated by commas. The values in a list do not need to be unique (the same value can be repeated). 

                                

items = ['cake', 'cookie', 'bread']
total_items = items + ['biscuit', 'tart']
print(total_items)  # Result: ['cake', 'cookie', 'bread', 'biscuit', 'tart']
Python Lists: Data Types

Lists can contain different data types, including numbers, strings, and even other lists. 

                                

numbers = [1, 2, 3, 4, 10]
names = ['Jenny', 'Sam', 'Alexis']
mixed = ['Jenny', 1, 2]
list_of_lists = [['a', 1], ['b', 2]]
List Method .append()

Use the .append() method to add an item to the end of a list. 

                                

orders = ['daisies', 'periwinkle']
orders.append('tulips')
print(orders)  # Result: ['daisies', 'periwinkle', 'tulips']
Zero-Indexing

List indexing in Python starts at 0. For adding one item at a time, use the .append() method. 

                                

names = ['Roger', 'Rafael', 'Andy', 'Novak']
List Indices

Access list elements by their index, starting from 0. 

                                

berries = ["blueberry", "cranberry", "raspberry"]
berries[0]  # "blueberry"
berries[2]  # "raspberry"
Negative List Indices

Negative indices access elements from the end of the list. 

                                

soups = ['minestrone', 'lentil', 'pho', 'laksa']
soups[-1]  # 'laksa'
soups[-3:]  # 'lentil', 'pho', 'laksa'
soups[:-2]  # 'minestrone', 'lentil'
Modifying 2D Lists

Modify elements in a 2D list by specifying the indices for sublists and their elements. 

                                

# A 2D list of names and hobbies
class_name_hobbies = [["Jenny", "Breakdancing"], ["Alexus", "Photography"], ["Grace", "Soccer"]]
class_name_hobbies[0][1] = "Meditation"
print(class_name_hobbies)  # Output: [["Jenny", "Meditation"], ["Alexus", "Photography"], ["Grace", "Soccer"]]
Accessing 2D Lists

Access elements in a 2D list using two indices: one for the sublist and one for the element within that sublist. 

                                

# 2D list of people's heights
heights = [["Noelle", 61], ["Ali", 70], ["Sam", 67]]
noelles_height = heights[0][1]
print(noelles_height)  # Output: 61
List Method .remove()

Remove the first occurrence of a value from a list using the .remove() method. 

                                

# Create a list
shopping_line = ["Cole", "Kip", "Chris", "Sylvana", "Chris"]
# Removes the first occurrence of "Chris"
shopping_line.remove("Chris")
print(shopping_line)  # Output: ["Cole", "Kip", "Sylvana", "Chris"]
Tuples

Tuples are immutable sequences of elements. They cannot be modified after creation. 

                                

my_tuple = ('abc', 123, 'def', 456, 789, 'ghi')
len(my_tuple)  # returns length of tuple
max(my_tuple)  # returns maximum value of tuple
min(my_tuple)  # returns minimum value of tuple
my_tuple.index(123)  # returns the position of the value 123
my_tuple.count('abc')  # returns the number of occurrences of 'abc'
List Method .count()

Count the occurrences of a specific value in a list using the .count() method. 

                                

backpack = ['pencil', 'pen', 'notebook', 'textbook', 'pen', 'highlighter', 'pen']
numPen = backpack.count('pen')
print(numPen)  # Output: 3
Determining List Length with len()

Find the number of items in a list using the len() function. 

                                

knapsack = [2, 4, 3, 7, 10]
size = len(knapsack)
print(size)  # Output: 5
List Method .sort()

Sort a list in ascending order using the .sort() method. 

                                

exampleList = [4, 2, 1, 3]
exampleList.sort()
print(exampleList)  # Output: [1, 2, 3, 4]
List Slicing

Slice a list to access a subset of its elements. 

                                

tools = ['pen', 'hammer', 'lever']
tools_slice = tools[1:3]  # ['hammer', 'lever']
tools_slice[0] = 'nail'
# Original list is unaltered:
print(tools)  # ['pen', 'hammer', 'lever']
sorted() Function

Sort a list and return a new sorted list using the sorted() function. 

                                

unsortedList = [4, 2, 1, 3]
sortedList = sorted(unsortedList)
print(sortedList)  # Output: [1, 2, 3, 4]
List Method .insert()

Insert an element at a specific position in a list using the .insert() method. 

                                

# Here is a list representing a line of people at a store
store_line = ["Karla", "Maxium", "Martim", "Isabella"]
# Insert "Vikor" after "Maxium" and before "Martim"
store_line.insert(2, "Vikor")
print(store_line)  # Output: ['Karla', 'Maxium', 'Vikor', 'Martim', 'Isabella']
List Method .pop()

Remove and return an element from a list using the .pop() method. 

                                

# Pop the last element
cs_topics = ["Python", "Data Structures", "Balloon Making", "Algorithms", "Clowns 101"]
removed_element = cs_topics.pop()
print(cs_topics)
print(removed_element)  # Output: ['Python', 'Data Structures', 'Balloon Making', 'Algorithms']
# 'Clowns 101'

Loops

break Keyword

The break keyword exits a loop immediately, regardless of the iteration number. 

                                

numbers = [0, 254, 2, -1, 3]
for num in numbers:
  if (num < 0):
    print("Negative number detected!")
    break
  print(num)  # 0
# 254
# 2
# Negative number detected!
Python List Comprehension

Create a list based on existing lists using a concise syntax. 

                                

# List comprehension for the squares of all even numbers between 1 and 10
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
even_squares = [x**2 for x in numbers if x % 2 == 0]
print(even_squares)  # Output: [4, 16, 36, 64, 100]
range() Function

Generate a sequence of numbers using the range() function, often used in loops. 

                                

for i in range(5):
  print(i)  # Output: 0, 1, 2, 3, 4
for Loop

Use a for loop to iterate over a sequence or a collection of items. 

                                

animals = ['cat', 'dog', 'rabbit']
for animal in animals:
  print(animal)  # Output: cat, dog, rabbit
while Loop

Use a while loop to execute code as long as a condition is true. 

                                

i = 0
while i < 5:
  print(i)
  i += 1  # Output: 0, 1, 2, 3, 4

Favourites

Monitor your IT infrastructure effortlessly with Site24x7 and get comprehensive insights and ensure smooth operations with 24/7 monitoring.

Sign up now Right Arrow

Programming Cheatsheets: Quick Reference for Productivity

Welcome to our comprehensive collection of programming language cheatsheets! Whether you're a seasoned developer or a beginner, these quick reference guides provide essential tips and key information for all major languages. They focus on core concepts, commands, and functions—designed to enhance your efficiency and productivity.

ManageEngine Site24x7, a leading IT monitoring and observability platform, is committed to equipping developers and IT professionals with the tools and insights needed to excel in their fields.

Monitor your IT infrastructure effortlessly with Site24x7 and get comprehensive insights and ensure smooth operations with 24/7 monitoring.

Sign up now! Right Arrow

Recent Releases

Blog IconBlogs
Learn IconLearn
Tools IconTools