** Special Usages
1. Unpacking a dictionary into keyword arguments in a function call
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| def greet(name, age):
print(f"Hello, {name}, You are {age} years old.")
person = {"name": "Alice", "age": 30}
greet(**person)
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Output:
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| Hello, Alice. You are 30 years old.
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2. Merging two dictionaries
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| dict1 = {"a": 1, "b": 2}
dict2 = {"b": 3, "c": 4}
merged_dict = {**dict1, **dict2}
print(merged_dict)
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Output:
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| {'a': 1, 'b': 3, 'c': 4}
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Notice that the overlapping key ‘b’, its value is overwritten by dict2.
* Special Usages
1. Unpacking Iterables
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| def add(a, b, c):
return a + b + c
nums = [1, 2, 3]
result = add(*nums)
print(result)
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Output:
2. Variable-Length Function Arguments
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| def print_all(*args):
for arg in args:
print(arg)
print_all(1, 2, 3, 4)
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Output:
3. Unpacking in Iterables
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| a = [1, 2, 3]
b = [*a, 4, 5]
print(b)
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Output:
4. Keyword-Only Arguments
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| def func(a, *, b):
return a + b
# func(1, 2) -> Error, func() takes 1 positional argument but 2 were given
func(1, b=2) # works
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5. List/Iterable Multiplication
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| repeated = [1, 2, 3] * 3
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BTW, be careful when using this syntactic sugar because it may create references to the same object.
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| repeated = [[1, 2, 3]] * 3
print(repeated)
repeated[0][0] = 6
print(repeated)
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References