Q:

Python program to sort a list of tuples by second item

mahmoud2506
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2022-05-23
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Example:

tuple = ("python", "includehelp", 43, 54.23)

Sorting a list of tuples by second item

In this program, we have a list of tuples and we need to sort the list of tuples by the index of sorting which will be the second item of the tuple.

We basically will use a sorting algorithm but instead of using the Ist value of the list, we will use the second element of the tuple.

Example:

Input:
[(2, 5), (9, 1), (4, 6), (2, 8), (1, 7)]

Output:
[(9, 1), (2, 5), (4, 6), (1, 7), (2, 8)]

In Python programming language, there are multiple ways to perform a single task in different ways and it totally depends on the programmer and then the need of the software being developed that which one should be used.

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All Answers

mahmoud2506
2022-05-23
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Method 1:

Using binary sorting technique for sorting. We will access the second element of the tuple as an index for sorting the list.

Program:

# Python program to sort a list of tuples by second item

# Creating a new tuple 
tupleList = [(2, 5), (9, 1), (4, 6), (2, 8), (1, 7)]
print("Unordered list : ", str(tupleList))

# Sorting the list of tuples using second item 
listLen = len(tupleList)
for i in range(0, listLen):
    for j in range(0, (listLen - i - 1)):
        if(tupleList[j][1] > tupleList[j+1][1]):
            temp = tupleList[j]
            tupleList[j] = tupleList[j+1]
            tupleList[j+1] = temp

# Printing sorted list 		
print("Sorted List : ", str(tupleList))

Output:

Unordered list :  [(2, 5), (9, 1), (4, 6), (2, 8), (1, 7)]
Sorted List :  [(9, 1), (2, 5), (4, 6), (1, 7), (2, 8)]

Method 2 : Using sorting methods

Python provides us with some built-in sorting methods. While using the sorting methods, we need to pass a method to the method which will swap the element to the second element of tuple.

Using sort() method

# Python program to sort a list of tuples by second item

# Creating a new tuple 
tupleList = [(2, 5), (9, 1), (4, 6), (2, 8), (1, 7)]
print("Unordered list : ", str(tupleList))

# Sorting the list of tuples using second item 
tupleList.sort(key = lambda val: val[1]) 

# Printing sorted list 		
print("Sorted List : ", str(tupleList))

Output:

Unordered list :  [(2, 5), (9, 1), (4, 6), (2, 8), (1, 7)]
Sorted List :  [(9, 1), (2, 5), (4, 6), (1, 7), (2, 8)]

Using sorted() method

# Python program to sort a list of tuples by second item

# Creating a new tuple 
tupleList = [(2, 5), (9, 1), (4, 6), (2, 8), (1, 7)]
print("Unordered list : ", str(tupleList))

# Sorting the list of tuples using second item 
sortedTuple  = sorted(tupleList, key = lambda val: val[1])

# Printing sorted list 		
print("Sorted List : ", str(sortedTuple))

Output:

Unordered list :  [(2, 5), (9, 1), (4, 6), (2, 8), (1, 7)]
Sorted List :  [(9, 1), (2, 5), (4, 6), (1, 7), (2, 8)]

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