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Python | Merging two list of dictionaries

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  • Last Updated : 12 Oct, 2021
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Given two list of dictionaries, the task is to merge these two lists of dictionaries based on some value.

Method #1: Using defaultdict and extend to merge two list of dictionaries based on school_id.




# Python code to  merge two list of dictionaries 
# based on some value.
  
from collections import defaultdict
  
# List initialization
Input1 = [{'roll_no': ['123445', '1212'], 'school_id': 1},
          {'roll_no': ['HA-4848231'], 'school_id': 2}]
  
Input2 = [{'roll_no': ['473427'], 'school_id': 2},
          {'roll_no': ['092112'], 'school_id': 5}]
  
  
# Using defaultdict
temp = defaultdict(list
  
# Using extend
for elem in Input1:
    temp[elem['school_id']].extend(elem['roll_no'])
  
for elem in Input2:
    temp[elem['school_id']].extend(elem['roll_no'])
  
Output = [{"roll_no":y, "school_id":x} for x, y in temp.items()]
  
# printing
print(Output)

Output:

[{‘school_id’: 1, ‘roll_no’: [‘123445’, ‘1212’]}, {‘school_id’: 2, ‘roll_no’: [‘HA-4848231’, ‘473427’]}, {‘school_id’: 5, ‘roll_no’: [‘092112’]}]

 
Method #2: Using extend() only.




# Python code to  merge two list of dictionaries 
# based on some value.
  
# List initialization
Input1 = [{'roll_no': ['123445', '1212'], 'school_id': 1},
          {'roll_no': ['HA-4848231'], 'school_id': 2}]
Input2 = [{'roll_no': ['473427'], 'school_id': 2},
          {'roll_no': ['092112'], 'school_id': 5}]
  
# Iterating and using extend to convert
for elm2 in Input2:
  
    for elm1 in Input1:
        if elm2['school_id'] == elm1['school_id']:
            elm1['roll_no'].extend(elm2['roll_no'])
            break
    else:
        Input1.append(elm2)
  
# printing 
print(Input1)

Output:

[{‘school_id’: 1, ‘roll_no’: [‘123445’, ‘1212’]}, {‘school_id’: 2, ‘roll_no’: [‘HA-4848231’, ‘473427’]}, {‘school_id’: 5, ‘roll_no’: [‘092112’]}]


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