Question

Search the Web for an example of list in Python code, share it, and post the link for the site.

Describe how it works in English as an algorithm, which is a sequence of simple steps.

Why do we use lists in Python? How do they differ from a dictionary?

Answer 1

Note: As per Chegg Policy we can't paste external links in answer section. So I will be giving my own example and algorithm and explanation.

Python List

List is a 1 of collection in python out of 4(List,Tuple,Set,Dictionary) . List is ordered and the value of list can be changed. Value in a list is referred by their index position. Index starts from 0(zero). List can hold duplicate values or elements.

Example

#declaring list of integers
mylist = [1, 2, 3,4,5,6,7,8,9]

#printing 3rd element from mylist
print(mylist[2])
#printing total length of mylist or total number of elements in mylist
print(len(mylist))
#checking whether value 9 is present in mylist
if 9 in mylist:
print("Number is Present")
else:
print("Number is Not Present")

#adding element 10 to mylist using append method
mylist.append(10)
print(mylist)

Output:

3                                                                                                                             

9                                                                                                                             

Number is Present                                                                                                             

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]  

Algorithm

• The above program first print 3 which is the 3rd element in list we access this by index 2(mylist[2]) ,
• then it prints 9 total number of elements in mylist using len (length method in python)
• Then we are checking whether 9 is present in mylist or not and printing corresponding values.
• last we add 10 to mylist using python built in method append and print all elements of mylist

Usage of List

List is mainly used when we doesn't need random access of data & is used when data are simple collection and are easily accessed through iteration instead of lookup.Lists are mainly used when we need slicing of data values.

Difference between List and Dictionary

• List is ordered but Dictionary is unordered
• List allows duplicate elements but Dictionary doesn't allow duplicates
• List uses index values starting from 0 to access elemets but dictionary uses key to access values
• List is declared as elements enclosed in square bracket but in dictionary values are enclosed in braces as key value pairs
• List allows slicing (printing few parts of list) but dictionary doesn't allow slicing