Walrus operator (:=): This operator allows you to assign and return a value in the same expression. It can be particularly useful in list comprehensions or other situations where you need to assign a value to a variable and use it in a subsequent expression. Here's an example:
if (n := len(my_list)) > 10:
print(f"List is too long ({n} elements, expected <= 10)")
Extended Iterable Unpacking: This feature allows you to unpack an iterable into multiple variables, including a "catch-all" variable that gets assigned any remaining items in the iterable. Here's an example:
first, *middle, last = my_list
In this example, first is assigned the first item in my_list, last is assigned the last item, and middle is assigned all the items in between.
Underscore as a placeholder: In interactive Python sessions, you can use the underscore (_) as a shorthand for the result of the last expression. This can be useful if you need to reuse the result of a previous command. Here's an example:
>>> 3 * 4
12
>>> _ + 5
17
slots attribute: The __slots__ attribute allows you to define the attributes of a class and their data types in advance, which can make the class more memory-efficient. Here's an example:
class MyClass:
__slots__ = ("x", "y")
def __init__(self, x, y):
self.x = x
self.y = y
In this example, we are defining a class with two attributes (x and y) and using the __slots__ attribute to define them in advance.
Callable instances: In Python, instances of classes can be made callable by defining a __call__ method. This can be useful if you want to create objects that behave like functions. Here's an example:
class Adder:
def __init__(self, n):
self.n = n
def __call__(self, x):
return self.n + x
add_five = Adder(5)
result = add_five(10)
print(result) # Output: 15
In this example, we are defining a class Adder that takes a number n and defines a __call__ method that adds n to its argument. We then create an instance of Adder with n=5 and use it like a function to add 5 to 10, resulting in 15.
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