Sunday 26 March 2023

5 awesome hidden features in Python

 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
>>> _ + 5

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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