list in python

list_python.markdown

Primitive Types in Python

Python has 4 primitive data types:

1. Integers (ex. 1, 2, 3)
2. Float (ex. 1.2, 2.5, 5.8)
3. Strings (ex. "Alexandria", "John", "Tony")
4. Boolean (True, False)

What is a list?

A list is a data structure in Python that is a mutable, or changeable, ordered sequence of elements.
They use [] brackets and commas to separate objects in the list.

Examples:

list_of_integers = [1, 2, 3, 4]   
list_of_strings = ["CA", "NY", "AL", "AK"]    
random_list = [1, 2 , "Hennery", "AR", 34.56]

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Examples:

list_of_integers = [1, 2, 3, 4]   
list_of_strings = ["CA", "NY", "AL", "AK"]    
random_list = [1, 2 , "Hennery", "AR", 34.56]

Access Elements in Python List (Indexing Lists)

• Each item in a list corresponds to an index number, which is an integer value, starting with the index number 0.
• we can also access items from the list with a negative index number, by counting backwards from the end of the list, starting at -1.

colors = ["Blue", "White", "Red"]
first_color = colors[0]
print(first_color)

white_color = colors[1]
print(white_color)
print(colors[-1])

Negative Element Index	-3	-2	-1
Positive Element Index	0	1	2
List Elements	"Red"	"Blue"	"White"

IndexError

If we call the list colors with an index number of any that is greater than 2, it will be out of range as it will not be valid:

colors = ["blue", "white", "red"]
print(colors[5])
# output: IndexError: list index out of range

Modifying Items in Lists

nums = [1, 2, 3, 4]
print(nums)
nums[3] = "John"
print(nums)

nums[-4] = 12.75
print(nums)

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#Deleting Items from List

1- Delete Element from python list using del keyword

nums = [1, 2, 3, 4]

del nums[1]
print(nums)

2- Delete last element from python list using pop() function

nums = [1, 2, 3, 4]

delete_element = nums.pop()

print(delete_element)
print(nums)

3- Delete elements by passing index to pop() function

nums = [1, 2, 3, 4]

delete_element = nums.pop(1)

print(delete_element)
print(nums)

4- Deleting all list elements using clear() function

nums = [1, 2, 3, 4]

nums.clear()
print(nums)

5- Delete element from python list using by passing value to remove() function

names_list = ["John", "Tony", "Mark"]

names_list.remove("John")
print(names_list)

6- Deleting range using del and slicing

nums = [1, 2, 3, 4, 5]
del nums[0:3]
print(nums)

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Adding Items to python List

1- Using append() function

my_list = ["Olivia", "Emma", "Sophia"]
my_list.append("Mia")
print(my_list)

2- Using insert() function

my_list = ["Olivia", "Emma", "Sophia"]
my_list.insert(0, "beginning")
my_list.insert(4, "end")
print(my_list)

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Modifying Lists with Operators

nums = [1, 2, 3]
days = ["Sat", "Sun", "Mon"]

c = nums + days
print(c)

a = nums + [4, 5, 6]
print(a)

print(nums * 2)

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Basic List Operations

my_list = [1, 1, 1, 2, 3, 4]
my_len = len(my_list)
print(my_len)

my_count = my_list.count(1)
print(my_count)

i = my_list.index(2)
print(i)

my_list.reverse()
print(my_list)

unsorted_list = [4, 6, 5, 2, 3, 1]
unsorted_list.sort()
print(unsorted_list)