reversed()

reversed() Signature

reversed(seq)

reversed() Examples

With tuples and lists as an argument:

>>> tuple(reversed((1, 2, 3, 4)))
(4, 3, 2, 1)
>>> list(reversed(["a", "b", "c", "d"]))
['d', 'c', 'b', 'a']

With a string as an argument:

>>> "".join(reversed("Hello, World!"))
'!dlroW ,olleH'

reversed() Common Use Cases

The most common use cases for the reversed() function include:

• Iterating over a sequence in reverse order without modifying the original data.
• Reversing lists of strings for display or processing.
• Creating a reversed copy of a sequence.

reversed() Real-World Example

Suppose you have a list of tasks that need to be processed in reverse order. You can use the reversed() function to iterate over the list from last to first:

>>> tasks = ["task1", "task2", "task3", "task4"]
>>> for task in reversed(tasks):
...     print("Processing", task)
...
Processing task4
Processing task3
Processing task2
Processing task1

In this example, reversed() allows you to efficiently process tasks in reverse order without altering the original list.

class FloatRange:
    def __init__(self, start, stop, step=1.0):
        if start >= stop:
            raise ValueError("Invalid range")
        self.start = start
        self.stop = stop
        self.step = step

    def __iter__(self):
        n = self.start
        while n < self.stop:
            yield n
            n += self.step

    def __reversed__(self):
        n = self.stop - self.step
        while n >= self.start:
            yield n
            n -= self.step

# Usage
for number in FloatRange(0.0, 2.0, 0.5):
    print(number)  # Output: 0.0 0.5 1.0 1.5

for number in reversed(FloatRange(0.0, 2.0, 0.5)):
    print(number)  # Output: 1.5 1.0 0.5 0.0