Consider a list:
list1 = [6,7,8,9]
What is the difference between the following operations on list1:
a) list1 * 2
b) list1 *= 2
c) list1 = list1 * 2

Question

Accepted Answer

> [!TLDR]
> All three produce the elements `[6, 7, 8, 9, 6, 7, 8, 9]`, but they differ in **what happens to `list1`**: (a) is a bare expression — `list1` is unchanged;
> (b) `*=` doubles the **same list object** in place;
> (c) `=` binds the name to a **brand-new** doubled list. The `id()` of the object tells them apart.

Starting each time from `list1 = [6, 7, 8, 9]`:

**a) `list1 * 2` — an expression, nothing stored**

```python
list1 = [6, 7, 8, 9]
print(list1 * 2)     # the computed value
print(list1)         # the original, untouched
```

```text
[6, 7, 8, 9, 6, 7, 8, 9]
[6, 7, 8, 9]
```

`*` on a list builds a **new** repeated list as a value. Written on its own line without assignment, that value is discarded — `list1` still has 4 elements.

**b) `list1 *= 2` — in-place repetition, same object**

```python
list1 = [6, 7, 8, 9]
before = id(list1)
list1 *= 2
print(list1)
print(id(list1) == before)
```

```text
[6, 7, 8, 9, 6, 7, 8, 9]
True
```

The augmented assignment `*=` modifies the **existing list object in place** (like `extend`-ing it with a copy of itself). The `id()` check proves it is still the *same* object — so any other variable pointing to this list sees the change too.

**c) `list1 = list1 * 2` — a new object rebound to the name**

```python
list1 = [6, 7, 8, 9]
before = id(list1)
list1 = list1 * 2
print(list1)
print(id(list1) == before)
```

```text
[6, 7, 8, 9, 6, 7, 8, 9]
False
```

Here the right side first builds a **new** doubled list, and the assignment then points the name `list1` at it. The original 4-element object is abandoned (and garbage-collected if nothing else references it). If another variable, say `alias = list1`, had been made before this line, `alias` would **still show the old 4-element list** — the visible difference from (b).

**Summary table** …

Student	Physics ( $x$ )	Chemistry ( $y$ )
A	85	90
B	70	65
C	55	55

Q.Consider a list:
list1 = [6,7,8,9]
What is the difference between the following operations on list1:

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Q.Consider a list: list1 = [6,7,8,9] What is the difference between the following operations on list1:

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Q.Consider a list:
list1 = [6,7,8,9]
What is the difference between the following operations on list1:

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