---
title: "datatype-dictionary (en)"
description: "Dictionaries: key:value storage — lookup, .items() looping, list values, keys as a list, and _ as the key name."
url: "https://aaronchan.com/kb/datatype-dictionary/"
updated: "2026-09-15"
category: "Code-Python (en)"
tags:
  - python
---

# datatype-dictionary (en)

A dictionary stores data as key:value pairs — you look up a value by its key. Here are 5 examples: basic lookup, looping over items (`.items()`), a list value, turning keys into a list (`list(dict.keys())`), and using `_` as the key name.

## Example 1: create a dict and read by key

 Copy

```
dict1={"key1":"john", "key2":"paul"}
print (dict1["key1"])
```

**output:**

```
john
```

---

## Example 2: loop over key and value (.items())

 Copy

```
my_dict = {'apple': 3, 'banana': 5, 'orange': 2}

for key, value in my_dict.items():
    print(f'{key} : {value}')
```

**output:**

```
apple : 3
banana : 5
orange : 2
```

---

## Example 3: value is a list

 Copy

```
dictStu = {'StuName': ['Ada, Billy, Cindy'], 'ChiScore': [10,20,30]}
for key in dictStu:
    print(f'{key}: {dictStu[key]}')
```

**output:**

```
StuName: ['Ada, Billy, Cindy']
ChiScore: [10, 20, 30]
```

---

## Example 4: turn keys into a list (list(dict.keys()))

 Copy

```
dictStu = {'StuName': 'Ada',
           'ChiScore': 'A'}
keys = list(dictStu.keys())
print(keys)

count=0
while (count<len(keys)):
    print (f'{keys[count]}:{dictStu[keys[count]]}')
    count=count+1
```

**output:**

```
['StuName', 'ChiScore']
StuName:Ada
ChiScore:A
```

---

## Example 5: use _ as the key name

 Copy

```
dict1 = {'aaa':111, 'bbb':222, 'ccc':333}
for _, value in dict1.items():
    print (f'key={_}, value={value}')
```

**output:**

```
key=aaa, value=111
key=bbb, value=222
key=ccc, value=333
```