---
title: "datatype-list (en)"
description: "list is Python's most common container. Wrapped in square brackets [], its items can be changed, can repeat, and keep their insertion order."
url: "https://aaronchan.com/kb/datatype-list/"
updated: "2026-09-15"
category: "Code-Python (en)"
---

# datatype-list (en)

list is Python's most common container. Wrapped in square brackets `[]`, its items can be changed, can repeat, and keep their insertion order.

Create a list first, then loop through it with `for`.

 Copy

```
my_list = [10, 20, 30, 40, 50]

for value in my_list:
    print(value)
```

**output:**

```
10
20
30
40
50
```

---

`append()` adds a new item to the end; `prices[1]` reads the second item by index (index starts at 0).

 Copy

```
prices = [100, 102, 99]
prices.append(105)  # 加到結尾
print(prices[1])  # 102（index 1）
```

**output:**

```
102
```

---

**pop(index): removes and returns the item at that index (defaults to the last one if omitted).**

 Copy

```
prices = [100, 102, 99, 105]
prices.pop(2)  # 移除 index 2 的 99，並回傳
print(prices)  # [100, 102, 105]
```

**output:**

```
[100, 102, 105]
```

---

**remove(value): deletes the first item equal to value.**

 Copy

```
prices = [100, 102, 99, 105]
prices.remove(99)  # 刪掉第一個 99
print(prices)  # [100, 102, 105]
```

**output:**

```
[100, 102, 105]
```

---

**del prices[index]: deletes by index, doesn't return anything.**

 Copy

```
prices = [100, 102, 99]
del prices[0]  # 刪掉 100
print(prices)  # [102, 99]
```

**output:**

```
[102, 99]
```

---

**Use sum() to add up and len() to count, to get the average.**

 Copy

```
race_times = [72.5, 74.2, 71.8, 73.1]
avg_time = sum(race_times) / len(race_times)
print(f"Average time: {avg_time:.1f}s")  # 72.9s
```

**output:**

```
Average time: 72.9s
```