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for ... in reversed()

for loop

reversed() returns an iterator that walks a sequence backwards. It works with lists, tuples, strings, ranges and any object with __reversed__.

Syntax

for item in reversed(sequence): ...

Unlike the slice sequence[::-1], reversed() copies nothing and returns a lazy iterator, saving memory on long sequences. That is also why it needs a real sequence (with a length and indexing, or __reversed__): you cannot pass a plain generator or a file object to reversed().

Examples

for x in reversed([1,2,3]): print(x, end=" ")  # → 3 2 1
print(list(reversed(range(5))))   # → [4, 3, 2, 1, 0]
for ch in reversed("abc"): print(ch, end="")  # → cba
t = (10, 20, 30)
for v in reversed(t): print(v, end=" ")  # → 30 20 10
print(list(reversed(["a","b","c"])))  # → ['c', 'b', 'a']

See also

Common errors

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