Double star in python syntax is most used for pack or unpack a dictionary.

In function call

It is used to unpack the dictionaries and pass items in the dictionary as keyword arguments to the function.

def function(a, b):
	return a + b

params = {'a': 1, 'b': 2}
print(function(**params)) # prints: 3

In function argument

It is used to allow the function to accept an arbitrary number of keyword arguments. These arguments are stored in a dictionary. Here's an example:

def function(**kwargs):
	for key, value in kwargs.items():
		print(f'{key}:{value}')

In dictionary merging

It is used to unpacks dictionaries and merge them into a single dictionary, where keys from later dictionaries override earlier ones if there's a conflict.

dict1 = {'a': 1, 'b': 2}
dict2 = {'b': 3, 'c': 4}
merged_dict = {**dict1, **dict2}
print(merged_dict) # prints: {'a': 1, 'b': 3, 'c': 4}