Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Python - Merge a Matrix by the Elements of First Column
When it is required to merge a matrix by the elements of first column, a simple iteration and list comprehension and ‘setdefault’ method is used.
Example
Below is a demonstration of the same −
my_list = [[41, "python"], [13, "pyt"], [41, "is"],[4, "always"], [3, "fun"]]
print("The list is :")
print(my_list)
my_result = {}
for key, value in my_list:
my_result.setdefault(key, []).append(value)
my_result = [[key] + value for key, value in my_result.items()]
print("The result is :")
print(my_result)Output
The list is : [[41, 'python'], [13, 'pyt'], [41, 'is'], [4, 'always'], [3, 'fun']] The result is : [[41, 'python', 'is'], [13, 'pyt'], [4, 'always'], [3, 'fun']]
Explanation
A list is defined and displayed on the console.
An empty dictionary is created.
The list is iterated over, and the key-value pair with same keys are joined together and appended to the dictionary.
A list comprehension is used to get the elements of the dictionary, and the key and the value are added.
This is assigned to a variable.
This is the output that is displayed on the console.
Updated on: 08-Sep-2021
227 Views
Advertisements