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python-3.xdeque

Python: modify a deque inside a function

I know that it is possible to modify a list inside a function by using assignment as followslis[:] = new_list, however the question is, is it possible to modify a deque inside a function as it is also an iterable? Of course without using return inside the function.

It not possible to use 'deq[:] = new_deq ' as it gives the following error: TypeError: sequence index must be integer, not 'slice'

Solution

  • deque does not support a slice as an index, so to achieve the effect of lis[:] = new_list with a deque, you can clear it first before extending it:

    from collections import deque

def f(q, new_list):
    q.clear()
    q.extend(new_list)

d = deque([1, 2])
f(d, [2, 3])
print(d)

    This outputs:

    deque([2, 3])