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Python List

For 5^th Semester Hons

Sumana Bandyopadhyay

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Creating List
Access, Modify and Delete list Elements
Merge Lists
Use the slicing syntax to operate on sublists
Loop over lists

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A list is a compound data type, you can group values together
A list contains items separated by commas and enclosed within square brackets ([]).
Lists are similar to arrays in C.
One difference between them is that the items belonging

to a list can be of different data type.

The values stored in a list can be accessed using the [ ] operator
Index starts at 0.

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What is the result of this code? nums = [5, 4, 3, 2, 1] print(nums[-2])

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>>> math = 45

>>> science = 23

>>> social = 28

>>> marksList = [math, science, social]

>>>

>>> print(marksList) [45, 23, 28]

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Create a list, areas, that contains the area of the hallway (hall), kitchen (kit), living room (liv), bedroom (bed) and bathroom (bath), in this order. Use the predefined variables.
Print areas with the print() function.

# area variables (in square meters)

hall = 11.25

kit = 18.0

liv = 20.0

bed = 10.75

bath = 9.50

# Create list areas

# Print areas

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SN	Function with Description
1	len(list) Gives the total length of the list.
2	max(list) Returns item from the list with max value.
3	min(list) Returns item from the list with min value.
4.	sum(list) Returns the sum of all elements of list

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Two List can be combined using +

operator.

We cannot add a integer with list using +

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Forming new lists with a repeating sequence using the multiplication operator:

Create a list of 5 elements with initial value as 0

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Insertion	Append(ele)	Add element at end of List
	Insert(index , ele)	Add element at given index
	Extend( seq )	Appends all the elements of seq to list

Deletion	Pop(index)	Delete element based on Index
Deletion	Remove(key)	Delete element based on key

	Count(key)	Returns the number of occurrences of key
	Index(key)	Returns the index of key element
	Sort	Sorts elements of List
	Reverse	Reverses elements of list

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We can add elements to list.
To add one element, use append method.
This adds an item to the end of an existing list.

mylist = [] mylist.append(5) mylist.append(8) mylist.append(12)

#prints [5,8,12]

print(mylist)

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insert(index, element)

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Insert the elements in sorted order.

Algorithm
If list is empty, append element to list.
If element is less than first element, insert front.
Traverse till current element is less than

element to insert or till end of list

Insert the element.

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We can add a series of elements using extend method or + operator.

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a = [1,2,3]
b = [4,5,6]
Understand the difference between
a.append(b) and
a.extend(b)

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To delete last element

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To delete element at specific Index

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Remove method takes the key element to delete and removes it if present.

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In all the previous methods, we were not able to determine the index where the key element is present.

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index() method finds the given element in a list and returns its position.
If the same element is present more than once, index() method returns its smallest/first position.
If not found, it raises

a ValueError exception indicating the element is not in the list.

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The index method finds the first occurrence of a list item and returns its index.