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Python – Convert List to key-value list by prefix grouping
  • Last Updated : 01 Aug, 2020

Given a list, convert it to consecutive key-value lists, grouping by prefix.

Input : test_list = [“GFG-1”, 4, 6, “GFG-2”, 3, “GFG-3”, 9, 2], temp = “GF”
Output : {‘GFG-1’: [4, 6], ‘GFG-2’: [3], ‘GFG-3’: [9, 2]}
Explanation : All grouped till next prefix.

Input : test_list = [“MRK-1”, 4, 6, “MRK-2”, 3, “MRK-3”, 9, 2], temp = “MR”
Output : {‘MRK-1’: [4, 6], ‘MRK-2’: [3], ‘MRK-3’: [9, 2]}
Explanation : All grouped till next prefix, “MR”.

Method : Using groupby() + startswith() + lambda

The combination of above functions can be used to solve this problem. In this, we employ grouping of all elements by prefix using groupby() and lambda functions assists in performing segregation of prefix for grouping.



Python3




# Python3 code to demonstrate working of 
# Convert List to key-value list by prefic grouping
# Using groupby() + startswith() + lambda
from itertools import groupby
  
# initializing list
test_list = ["GFG-1", 4, 6, 7, "GFG-2", 2, 3, "GFG-3", 9, 2, 4, 6]
  
# printing original list
print("The original list : " + str(test_list))
  
# initializing prefix 
temp = "GFG"
  
res = {}
# extracting result from grouped by prefix
for key, val in groupby(test_list, lambda ele: str(ele).startswith(temp)):
      
    # checking for existing key 
    if key:
        k = next(val)
    else:
        res[k] = list(val)
          
# printing result 
print("The constructed dictionary : " + str(res))
Output
The original list : ['GFG-1', 4, 6, 7, 'GFG-2', 2, 3, 'GFG-3', 9, 2, 4, 6]
The constructed dictionary : {'GFG-1': [4, 6, 7], 'GFG-2': [2, 3], 'GFG-3': [9, 2, 4, 6]}

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