Python | Group tuples in list with same first value

Given a list of tuples, the task is to print another list containing tuple of same first element. Below are some ways to achieve above tasks.

Example:

Input : [('x', 'y'), ('x', 'z'), ('w', 't')]

Output: [('w', 't'), ('x', 'y', 'z')]

Method #1: Using extend

# Python code to find common  
# first element in list of tuple 
  
# Function to solve the task 
def find(Input): 
    out = {} 
    for elem in Input: 
        try: 
            out[elem[0]].extend(elem[1:]) 
        except KeyError: 
            out[elem[0]] = list(elem) 
    return [tuple(values) for values in out.values()] 
  
# List initialization 
Input = [('x', 'y'), ('x', 'z'), ('w', 't')] 
  
# Calling function 
Output = (find(Input)) 
  
# Printing 
print("Initial list of tuple is :", Input) 
print("List showing common first element", Output) 

Output:

Initial list of tuple is : [('x', 'y'), ('x', 'z'), ('w', 't')]
List showing common first element [('w', 't'), ('x', 'y', 'z')]

Method #2: Using defaultdict

# Python code to find common first 
# element in list of tuple 
  
# Importing 
from collections import defaultdict 
  
# Function to solve the task 
def find(pairs): 
    mapp = defaultdict(list) 
    for x, y in pairs: 
        mapp[x].append(y) 
    return [(x, *y) for x, y in mapp.items()] 
  
# Input list initialization 
Input = [('p', 'q'), ('p', 'r'), 
         ('p', 's'), ('m', 't')] 
  
# calling function 
Output = find(Input) 
  
# Printing 
print("Initial list of tuple is :", Input) 
print("List showing common first element", Output) 

Output:

Initial list of tuple is : [('p', 'q'), ('p', 'r'), ('p', 's'), ('m', 't')]
List showing common first element [('m', 't'), ('p', 'q', 'r', 's')]

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