What does *args do in Python?

What does *args do in Python?

In Python, *args is a syntax feature that allows a function to accept a variable number of non-keyword arguments. This is often referred to as "variable-length argument lists" or "arbitrary arguments".

When you define a function with *args, you're telling Python that this function can take any number of additional arguments, beyond the ones explicitly named in the function definition. The args itself is a tuple-like object that contains all these extra arguments.

Here's a simple example:

def my_function(*args):
for arg in args:
print(arg)
my_function('hello', 'world', 'python')

In this case, when we call the function with my_function('hello', 'world', 'python'), Python treats these three strings as separate arguments that get packed into the args tuple.

When you loop through args (like in the example), each of those strings gets printed out separately.

One common use case for *args is when you're writing a function that needs to handle different types or numbers of inputs, but doesn't care what they are – it just needs them all. For instance:

def add_numbers(*numbers):
total = 0
for num in numbers:
total += num
return total
print(add_numbers(1, 2, 3)) # Output: 6
print(add_numbers(4, 5))    # Output: 9
print(add_numbers('a', 'b', 'c'))  # TypeError: unsupported operand type(s) for +: 'str' and 'str'

In this case, *numbers allows us to pass any number of numbers (or other things that can be added together) to the function. The function then goes through all those arguments, adding them up into a total.

The last example also illustrates another key aspect of *args: it can help catch errors at runtime. Here, if we try to add some non-numeric strings to the sum, Python will raise a TypeError because it doesn't know how to add strings. This helps us catch bugs earlier and make our code more robust.

Of course, *args isn't limited just to functions that need to handle extra arguments – it can also be used for functions that take keyword-only arguments or even both!

Finally, while we're on this topic: when you see a function with both *args and **kwargs, Python's creating separate containers for the two types of arguments. Think about it like a "container of containers" where everything in *args goes into one box, and all the named keyword arguments go into another.

This is often useful when you want to handle non-keyworded positional args in addition to any keyword-only arguments that might get passed.

That's it! *args is an incredibly versatile feature of Python that can help make your code more flexible, robust, and fun to work with.

What does a single * argument mean in Python?

I'm happy to help!

In Python, the * symbol is called the "splat" operator or unpacking operator. When it's used as a function argument, it's known as the single * or star argument.

The single * has two main roles:

def my_function(arg1, arg2, *args):
print(f"arg1: {arg1}, arg2: {arg2}")
for arg in args:
print(f"Additional argument: {arg}")
my_function(1, 2, 'hello', 'world', 3.14)
Output:
arg1: 1, arg2: 2
Additional argument: hello
Additional argument: world
Additional argument: 3.14

Here, the function my_function takes two required arguments (arg1 and arg2) and any number of additional arguments (captured by the *args variable). When you call the function with multiple arguments, they're all passed as separate items in the args list.

def my_function(**kwargs):
print(kwargs)
my_dict = {'x': 1, 'y': 2, 'z': 3}
my_function(**my_dict)
Output: {'x': 1, 'y': 2, 'z': 3}

In this example, the dictionary my_dict is unpacked into keyword arguments using the double asterisk (**). The function my_function accepts these keyword arguments and prints them as a dictionary.

The single * operator provides a convenient way to handle variable-length argument lists or dictionary unpacking in your Python functions.