What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Use Python’s multiple-assignment syntax to swap two list elements in place: items[i], items[j] = items[j], items[i]. The indexes identify the positions to exchange, and Python lists count positions from zero.
Swap two list elements with one statement
Here is a complete example that exchanges the elements at indexes 1 and 3:
items = [10, 20, 30, 40]
i, j = 1, 3
items[i], items[j] = items[j], items[i]
print(items) # [10, 40, 30, 20]The right side supplies the two values in reversed order; the left side assigns them to the selected positions. Python describes this as multiple assignment combining tuple packing and sequence unpacking. Python’s data structures tutorial explains the assignment behavior, and the language reference documents subscriptions as assignment targets.
What the statement changes
This operation changes the existing list; it does not create a replacement list. Indexed assignment updates an element of the mutable list. Python’s informal introduction explains that assignment does not copy the underlying data.
#1 Best Overall
For example, if another variable refers to the same list, it will observe the swapped contents too:
items = ["red", "blue"]
alias = items
items[0], items[1] = items[1], items[0]
print(alias) # ["blue", "red"]Use a temporary variable for an explicit version
If separate steps make the exchange easier to follow, save one value before overwriting its position:
temp = items[i]
items[i] = items[j]
items[j] = tempThis also mutates the original list. The tuple-unpacking form is more concise; choose based on which is clearer for the reader or codebase.
Indexes and common edge cases
- Indexes start at zero. In a four-element list, valid positive indexes are
0,1,2, and3. - Negative indexes count from the end. For example,
items[-1]selects the final element. - Invalid indexes raise
IndexError. An assignment to an out-of-range list position fails; it does not append a new element. - The same index can be used twice. If
i == j, the element is assigned back to its own position, so the list’s contents do not change.
These index and assignment rules are covered in the Python language reference.
Free tools Windows power users keep installed
One-click scans. No signup required.
Lists are mutable; tuples are not
The indexed swap works because lists allow item assignment. A tuple is immutable, so assigning to tuple positions this way raises TypeError. If you need to change values, convert the tuple to a list first; if you need a new tuple, construct one with the desired order instead. See the Python data structures tutorial for the distinction.
Validate indexes when they come from input
If indexes come from a user or another untrusted source, decide whether your program accepts negative indexes. To allow only positions from zero through the final list index, check them before swapping:
if not (0 <= i < len(items) and 0 <= j < len(items)):
raise IndexError("list index out of range")
items[i], items[j] = items[j], items[i]For an empty list, no index passes this check. If negative indexes are intended, omit the nonnegative restriction and handle values below -len(items) or at least len(items) as invalid.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →
