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Python – Create dictionary from the list

  • Last Updated : 01 Oct, 2020

Given a list. The task is to convert it to a dictionary with the values as the list element and keys as the concatenation of the given string K and value.

Examples:

Input : test_list = [“gfg”, “is”, “best”], K = “pref_” 
Output : {‘pref_gfg’: ‘gfg’, ‘pref_is’: ‘is’, ‘pref_best’: ‘best’} 
Explanation : Keys constructed after concatenating K.

Input : test_list = [“gfg”, “best”], K = “pref_” 
Output : {‘pref_gfg’: ‘gfg’, ‘pref_best’: ‘best’} 
Explanation : Keys constructed after concatenating K. 

Method #1: Using loop



This is one of the ways in which this task can be performed. In this, we perform concatenation using + operator to construct keys and values are extracted from list.

Python3




# Python3 code to demonstrate working of 
# Values derived Dictionary keys
# Using loop
  
# initializing list
test_list = ["gfg", "is", "best"
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K 
K = "def_key_"
  
# using loop to construct new Dictionary
# + operator used to concat default key and values 
res = dict()
for ele in test_list:
    res[K + str(ele)] = ele 
  
# printing result 
print("The constructed Dictionary : " + str(res))

Output:

The original list is : [‘gfg’, ‘is’, ‘best’]
The constructed Dictionary : {‘def_key_gfg’: ‘gfg’, ‘def_key_is’: ‘is’, ‘def_key_best’: ‘best’}

Method #2: Using dictionary comprehension

This is yet another way in which this task can be performed. In this, we construct a dictionary using one-liner using dictionary comprehension.

Python3




# Python3 code to demonstrate working of 
# Values derived Dictionary keys
# Using dictionary comprehension
  
# initializing list
test_list = ["gfg", "is", "best"
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K 
K = "def_key_"
  
# using dictionary comprehension
# + operator used to concat default key and values 
res = {K + str(ele) : ele for ele in test_list}
  
# printing result 
print("The constructed Dictionary : " + str(res))

Output:

The original list is : [‘gfg’, ‘is’, ‘best’]
The constructed Dictionary : {‘def_key_gfg’: ‘gfg’, ‘def_key_is’: ‘is’, ‘def_key_best’: ‘best’}

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