Python Tutorial

One of the most important and widely used data structures within Python programming is the dictionary. When using Python to programme, it is not unusual to want to mix two or more dictionaries. In this article, we shall examine various approaches, examples, and results for merging two dictionaries in various contexts. But first, let's take a quick glance at the list of Python dictionaries below.

Unlike other data structure that holds the data as just a single value element, a dictionary is an unsorted collection of data pieces stored in key-value pairs. By inserting the key-value pair between the curly brackets () and a comma, you may build a dictionary (,). Moreover, a semicolon (:) is used to demarcate the value and key elements. Python's dictionaries are sorted, modifiable, and do not support duplication.

Dictionary keys are therefore immutable because there cannot be two objects in the dictionary with the same key. Dictionary keys are also case-sensitive, so words with the same identity but specific key types will be treated as separate data pieces.

The seven common methods to combine two dictionaries in Python are listed below:

Using the Method update():

The update() function in Python can be used to combine two dictionaries. The first dictionary is combined with the second one using this technique by being overwritten. Thus, it returns None and no fresh dictionary is formed. The result of the second dictionary will be rewritten if both dictionaries have the same key but different values.

d_1 = {'A': 15, 'B': 10, 'C' : 12 }
d_2 = {'E': 18,'B': 20,'D' : 16 }
d_1.update(d_2)
print('Updated dictionary:')
print(d_1)

Output

{'A': 15, 'B': 20, 'C': 12, 'E': 18, 'D': 16}

Utilizing the Merge '|' Operator

Using the | operator, two dictionaries can be combined. This is a very practical way for merging dictionaries; however, it can only be used with Python 3.9 or later.

def Merge(d_1, d_2):
	result = d_1 | d_2
	return result
dict_1 = {'A': 15, 'B': 10, 'C' : 12 }
dict_2 = {'E': 18,'B': 20,'D' : 16 }
d3 = Merge(dict_1, dict_2)
print(d3)

Output

{'A': 15, 'B': 20, 'C': 12, 'E': 18, 'D': 16}

Use of the ** Operator

The unpack operator (**) in Python is the simplest method for merging two dictionaries. The dictionary expands its content, which is a collection of key-value pairs, by using the "**" operator.

dict_1 = {'A': 15, 'B': 10, 'C': 12}
print(dict(**dict_1))

Output

{'A': 15, 'B': 10, 'C': 12}

Now, we'll use the symbol "**" to merge two dictionaries, and we'll use a third dictionary to record the result. The "**" operator will be used to expand the information in dict 1 and dict 2 before combining them to create dict 3. Similar to a update method, the output data will include the value from the second dictionary if both dictionaries have the same key but different values.

dict_1 = {'A': 15, 'B': 10, 'C' : 12 }
dict_2 = {'E': 18,'B': 20,'D' : 16 }
d3 = {**dict_1,**dict_2}
print(d3)

Output

{'A': 15, 'B': 20, 'C': 12, 'E': 18, 'D': 16}

Opening the Additional Dictionary

You can combine the two dictionaries and also get your final output by unpack the second dictionary with the "**" operator. Due to the requirement that the values of a second dictionary must be strings, this approach is not widely used or advised. Any time an int value appears, the "TypeError" method will be invoked.

dict_1={'A': 15, 'B': 10, 'C' : 12 }
dict_2={'E': 18,'B': 20,'D' : 16 }
d3=dict(dict_1,**dict_2)
print (d3)

Output

{'A': 15, 'B': 20, 'C': 12, 'E': 18, 'D': 16}

Employing collecting Chain Map() Procedure

One of the less well-known techniques for merging the two dictionaries using Python is this one. The collections modules from Chain Map library must be used in this function in order to gather various dictionaries into a single view. The value of first dictionary is obtained in the output if both dictionaries contain the same key(s).

from collections import ChainMap
dict_1={'A': 15, 'B': 10, 'C' : 12 }
dict_2={'E': 18,'B': 20,'D' : 16 }
d3 = ChainMap(dict_1, dict_2)
print(d3)
print(dict(d3))

Output

ChainMap({'A': 15, 'B': 10, 'C': 12}, {'E': 18, 'B': 20, 'D': 16})
{'E': 18, 'B': 10, 'D': 16, 'A': 15, 'C': 12}

Increase Common Key Values

In all of the aforementioned ways, the numbers in the final result were being overridden if both dictionaries included different data values for the same keys. What if you want to keep every bit of value in the output? You can combine the dictionaries for this purpose so that the final output is returned and the values of the similar keys are added to the list.

To iterate through values and keys in the dictionary contained within the function using this way, we will also utilise a for loop. The function will be used later to produce the combined dictionaries displayed below as the final output.

dict_1 = {'A': 15, 'B': 10, 'C': 12}
dict_2 = {'E': 18, 'B': 20, 'D': 16}
def mergeDictionary(dict_1, dict_2):
   d3 = {**dict_1, **dict_2}
   for key, value in d3.items():
       if key in dict_1 and key in dict_2:
               d3[key] = [value , dict_1[key]]
   return d3
d3 = mergeDictionary(dict_1, dict_2)
print(d3)

Output

{'A': 15, 'B': [20, 10], 'C': 12, 'E': 18, 'D': 16}

Using many dictionaries at once is among the frequent Python programming scenarios. However, if you are unsure of how to combine one or more dictionaries, it might be a tedious operation. As a result, we have provided a variety of techniques for merging dictionaries in Python under diverse circumstances.

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