Python Dictionary vs JSON

If you’ve ever worked with Python web frameworks like FastAPI or Django, you’ve likely seen how often dict and JSON are used interchangeably. At first glance, they look almost identical—but they’re not the same.

In this post, we’ll clearly explain the differences between a Python dictionary and a JSON object, when to use each, and how to convert between them effectively.

Definitions

Aspect	Python Dictionary	JSON (JavaScript Object Notation)
Language Type	Native Python object	String-based data format
Syntax	{'key': 'value'}	{"key": "value"}

Key Differences

• String Representation
  A Python dict is an actual data structure in memory, while JSON is just a text string.

• Quotation Marks
  Python allows both single and double quotes, but JSON strictly requires double quotes around keys and string values.

data = {'name': 'DS2Man', 'age': 30}
print(type(data)) # <class 'dict'>
print(data) # {'name': 'DS2Man', 'age': 30} # Note. single or double quotation

import json
dict2json = json.dumps(data)
print(type(dict2json)) # <class 'str'>
print(dict2json) # {"name": "DS2Man", "age": 30} # Note. must double quotation

How to Convert Between Them

Convert dict to JSON

import json

data = {'name': 'DS2Man, 데투남', 'age': 30}
print(type(data)) # <class 'dict'>
print(data) # {'name': 'DS2Man, 데투남', 'age': 30} # Note. single or double

dict2json = json.dumps(data) # default : ensure_ascii=True
print(type(dict2json)) # <class 'str'>
print(dict2json) # {"name": "DS2Man, \ub370\ud22c\ub0a8", "age": 30} # Note. must double

dict2json = json.dumps(data, ensure_ascii=False)
print(type(dict2json)) # <class 'str'>
print(dict2json) # {"name": "DS2Man, 데투남", "age": 30} # Note. must double

You can use the ensure_ascii option to convert Unicode characters into ASCII representations.

Option	Description
ensure_ascii=True (default)	Escapes all non-ASCII (Unicode) characters into ASCII (e.g., “한글” → \ud55c\uae00)
ensure_ascii=False	Outputs Unicode characters as-is without escaping (e.g., “한글” → 한글)

Convert JSON to dict

import json

json2dict = json.loads(dict2json)
print(type(json2dict))  # <class 'dict'>
print(json2dict)  # {'name': 'Alice', 'age': 30}