Differentiate between append() and extend() methods of list.

Question

Accepted Answer

> [!TLDR]
> `append(x)` adds its argument as **one single element** (even if it's a list — it gets nested); `extend(iterable)` iterates over its argument and adds **each element separately**. After adding a 2-element list, `append` grows the list by 1, `extend` by 2.

**Side-by-side demonstration:**

```python
list1 = [10, 20, 30]
list2 = [10, 20, 30]

list1.append([40, 50])    # one nested element in
list2.extend([40, 50])    # two separate elements in

print("append:", list1, "-> length", len(list1))
print("extend:", list2, "-> length", len(list2))
```

```text
append: [10, 20, 30, [40, 50]] -> length 4
extend: [10, 20, 30, 40, 50] -> length 5
```

**The differences, point by point**

| Aspect | `append(x)` | `extend(iterable)` |
|---|---|---|
| What it adds | `x` as **one** element, whatever it is | **every element** of the iterable, one by one |
| Length grows by | exactly 1 | `len(iterable)` |
| Passing a list | the list is **nested** inside | its elements are **merged** in flat |
| Argument type | anything (int, string, list, …) | must be an iterable (list, string, tuple, …) |
| In place? | yes, returns `None` | yes, returns `None` |

**Why the difference matters**

- `list1.append([40, 50])` makes `list1[3]` the *list* `[40, 50]` — to reach 40 you'd write `list1[3][0]`. Usually that nesting is an accident, caused by using `append` where `extend` was meant. …

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

Q.Differentiate between append() and extend() methods of list.

Concept understanding — List Method Differences

List Method Differences — From Intuition to Precision

The Precise Statement

Why This Matters

A Concrete Example

Aspect	`append(x)`	`extend(iterable)`
What it adds	`x` as one element, whatever it is	every element of the iterable, one by one
Length grows by	exactly 1	`len(iterable)`
Passing a list	the list is nested inside	its elements are merged in flat
Argument type	anything (int, string, list, …)	must be an iterable (list, string, tuple, …)
In place?	yes, returns `None`	yes, returns `None`

Q.Differentiate between append() and extend() methods of list.

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