How to switch position of two items in a Python list?

Swap items with unknown positions

When the positions of the items to be swapped are not known beforehand, list.index and parallel assignments can be applied:

idx1 = my_list.index('unknown1')  # Finds Waldo
idx2 = my_list.index('unknown2')  # Finds Carmen Sandiego
my_list[idx1], my_list[idx2] = my_list[idx2], my_list[idx1]  # Swaps their hideouts
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Above code will look for the indexes of 'unknown1' and 'unknown2' before swapping them. Swift and efficient, don't you think?

Swap using slicing

Let's mix things up a bit for adjacent items. Here, slicing works like a charm:

my_list[1:3] = my_list[1:3][::-1]  # Pulls a Back to the Future trick
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Just like that, we've reversed the slice with elements at index 1 and 2.

The tuple assignment charm

No indexes? No problem! Harness the magic of tuple unpacking:

idx1, idx2 = (my_list.index('obscure1'), my_list.index('obscure2'))  # Pairs Sherlock and Watson
my_list[idx1], my_list[idx2] = my_list[idx2], my_list[idx1]  # Swaps their disguises
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Voila! A graceful swap, infused with the elixir of tuple unpacking.

Classic swap with a sidekick

Introduce a temporary variable for a timeless twist to swapping:

sidekick = my_list[idx1]  # Robin, hold this.
my_list[idx1] = my_list[idx2]  # Batman, here's your mask.
my_list[idx2] = sidekick  # Robin, give me back my mask.
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A classic three-step dance that's intuitively attractive to Python initiates.

Optimized swap for a single showdown

If a list is expecting only one swap, optimize it to finish faster than a cowboy's duel:

items_to_swap = ('mystery1', 'mystery2')
for item in my_list:
    if item in items_to_swap:
        idx1, idx2 = my_list.index(items_to_swap[0]), my_list.index(items_to_swap[1])
        my_list[idx1], my_list[idx2] = my_list[idx2], my_list[idx1]
        break  # Exits the gunfight after disabling the villain
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