The fromkeys() function in Python is used to create a dictionary using specified keys and values. For example:

k = ("one", "two", "three")
v = 100

dOne = dict.fromkeys(k, v)
print(dOne)

dTwo = dict.fromkeys(k)
print(dTwo)

The output will be:

{'one': 100, 'two': 100, 'three': 100}
{'one': None, 'two': None, 'three': None}

Python fromkeys() function syntax

The syntax of the fromkeys() function in Python is:

dict.fromkeys(keys, value)

where "keys" refers to an iterable that specifies the keys, whereas "value" refers to a value to set for all the keys.

Note: The first parameter (keys) is required, whereas the second parameter (value) is optional.

Python fromkeys() Function Example

Here is an example of the fromkeys() function in Python.

d = dict.fromkeys([12, 432, 45, 5, 6, 34])
print(d)

The output will be:

{12: None, 432: None, 45: None, 5: None, 6: None, 34: None}

Advantages of the fromkeys() function in Python

• Simplify Code: fromkeys() eliminates the need to loop to initialize a dictionary with default values. This simplifies code.
• Efficient: fromkeys() creates a new dictionary with pre-defined values, making it more efficient than loop-initializing a dictionary with default values. This helps with large dictionaries.
• Customizable: fromkeys() lets you set all dictionary keys' default values. You can personalize the dictionary.

Disadvantages of the fromkeys() function in Python

• Limited functionality: You can only set a single default value for each key in the dictionary using the fromkeys() function. As a result, it cannot be used to create dictionaries with various default values for various keys.
• Limited functionality: You can only set a single default value for each key in the dictionary using the fromkeys() function. As a result, it cannot be used to create dictionaries with various default values for various keys.
• Only a sequence of keys can be used when creating a dictionary with fromkeys(). This implies that you are unable to create a dictionary using a class or function as the keys instead of a standard data type.
• Fromkeys() is ineffective for building complex data structures that require more than just a straightforward default value. You will have to use different functions or write custom code to initialize more intricate data structures.

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