Answer: Two dictionaries can be merged using the update() method, which modifies the original dictionary in place.
Merging dictionaries is important to combine the data from different sources. It also helps in updating if the same key exists in both dictionaries. In this blog, let’s discuss the multiple approaches to merging two dictionaries into a single expression in Python.
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Methods to Merge or Concatenate Two Dictionaries in Python
Merging or concatenation of two dictionaries is a very common task in Python. For this, Python provides various built-in methods and operators that can be used to merge or concatenate two dictionaries in Python:
Method 1: Using for loop in Python
The way it operates is by repeatedly adding key-value pairs from one dictionary to another. It will not work well though, when working with a big dataset.
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Method 2: Using | operator in Python
This is the merge operator, which creates a new dictionary without changing the ones that already exist. The value from the second dictionary replaces the first one if there is a duplicate key.
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Note: “The | operator is available only in Python 3.9 and later. If you’re using an older version, use update() or dict(**d1, **d2) instead.”
Method 3: Using update() and copy() function in Python
The update() function handles updating key-value pairs between two dictionaries. It works by copying dict_2 to dict_3 and using dict_1 to update dict_3.
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Method 4: Using |= operator in Python
It is an in-place dictionary merging method and multiple dictionaries can be merged using |= operator.
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Method 5: Using dict() constructor in Python
The dict() constructor can be used to create a new dictionary by copying the elements from the first dictionary and updating it with the second dictionary, combining both.
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Method 6: Using chain() method in Python
In this method, the chain() creates an iterable, and then dict() is used to convert it into a merged dictionary.
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Method 7: Using Chainmap() method in Python
The ChainMap() groups multiple dictionaries into a single view. However, modifications to the original dictionaries will be reflected in the ChainMap view.
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Method 8: Using unpacking in Python
By using the unpacking operator, multiple dictionaries can be merged into one, retaining their original contents. When using ** unpacking, duplicate keys will be replaced by values from the second dictionary. This method does not modify the dictionaries in place.
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Conclusion
The above-discussed method is used to merge two dictionaries or even multiple dictionaries. Understanding these methods helps merge two dictionaries in a single expression effectively in Python.