Flatten given list of dictionaries in Python

We have a list whose elements are dictionaries. We need to flatten it to get a single dictionary where all these list elements are present as key-value pairs.

With for and update

We take an empty dictionary and add elements to it by reading the elements from the list. The addition of elements is done using the update function.

Example

listA = [{'Mon':2}, {'Tue':11}, {'Wed':3}]
# printing given arrays
print("Given array:\n",listA)
print("Type of Object:\n",type(listA))
res = {}
for x in listA:
   res.update(x)
# Result
print("Flattened object:\n ", res)
print("Type of flattened Object:\n",type(res))

Output

Running the above code gives us the following result −

('Given array:\n', [{'Mon': 2}, {'Tue': 11}, {'Wed': 3}])
('Type of Object:\n', )
('Flattened object:\n ', {'Wed': 3, 'Mon': 2, 'Tue': 11})
('Type of flattened Object:\n', )

With reduce

We can also use the reduce function along with update function to read the elements from the list and add it to the empty dictionary.

Example

from functools import reduce
listA = [{'Mon':2}, {'Tue':11}, {'Wed':3}]
# printing given arrays
print("Given array:\n",listA)
print("Type of Object:\n",type(listA))
# Using reduce and update
res = reduce(lambda d, src: d.update(src) or d, listA, {})
# Result
print("Flattened object:\n ", res)
print("Type of flattened Object:\n",type(res))

Output

Running the above code gives us the following result −

('Given array:\n', [{'Mon': 2}, {'Tue': 11}, {'Wed': 3}])
('Type of Object:\n', )
('Flattened object:\n ', {'Wed': 3, 'Mon': 2, 'Tue': 11})
('Type of flattened Object:\n', )

With ChainMap

The ChainMap function will read each element from the list and create a new collection object but not a dictionary.

Example

from collections import ChainMap
listA = [{'Mon':2}, {'Tue':11}, {'Wed':3}]
# printing given arrays
print("Given array:\n",listA)
print("Type of Object:\n",type(listA))
# Using reduce and update
res = ChainMap(*listA)
# Result
print("Flattened object:\n ", res)
print("Type of flattened Object:\n",type(res))

Output

Running the above code gives us the following result −

Given array:
[{'Mon': 2}, {'Tue': 11}, {'Wed': 3}]
Type of Object:

Flattened object:
ChainMap({'Mon': 2}, {'Tue': 11}, {'Wed': 3})
Type of flattened Object: