json.dumps() in Python

Last Updated : 13 Jan, 2026

The json.dumps() function in Python converts a Python object (such as a dictionary or list) into a JSON-formatted string. It is mainly used when you need to send data over APIs, store structured data or serialize Python objects into JSON text.

Example: This example shows how to convert a Python dictionary into a JSON string.

Python 
import json
d = {"a": "Hello", "b": "World"}
s = json.dumps(d)
print(s)
print(type(s))

Output
{"a": "Hello", "b": "World"}
<class 'str'>

Explanation:

  • json.dumps(d) converts the dictionary d into a JSON string.
  • The output type is str, not a dictionary.

Syntax

json.dumps(obj, skipkeys=False, ensure_ascii=True, allow_nan=True, indent=None, separators=None, sort_keys=False)

Parameters:

  • obj: Python object to convert (dict, list, string, etc.)
  • skipkeys: Ignores unsupported keys instead of raising an error
  • ensure_ascii: Escapes non-ASCII characters if True
  • allow_nan: Allows NaN, Infinity values
  • indent: Formats JSON with indentation
  • separators: Custom separators for items and key–value pairs
  • sort_keys: Sorts dictionary keys alphabetically

Return Type: string object (str).

Examples

Example 1: This example demonstrates how skipkeys=True ignores dictionary keys that are not JSON-compatible.

Python 
import json
d = {("x", "y"): 10, "a": 1}
s = json.dumps(d, skipkeys=True)
print(s)

Output
{"a": 1}

Explanation:

  • JSON does not support tuple keys.
  • skipkeys=True removes invalid keys automatically.

Example 2: This example formats JSON output to make it more readable using indentation.

Python 
import json
d = {"a": 1, "b": 2, "c": 3}
s = json.dumps(d, indent=4)
print(s)

Output
{
    "a": 1,
    "b": 2,
    "c": 3
}

Explanation:

  • indent=4 adds spacing and line breaks.
  • The JSON string becomes easy to read.

Example 3: This example sorts dictionary keys alphabetically before converting them to JSON.

Python 
import json
d = {"c": 3, "a": 1, "b": 2}
s = json.dumps(d, sort_keys=True)
print(s)

Output
{"a": 1, "b": 2, "c": 3}

Explanation:

  • sort_keys=True sorts keys alphabetically.
  • Useful for consistent JSON output.

Example 4: This example shows how json.dumps() converts a Python list into a JSON-formatted string, which is commonly used when sending list data through APIs.

Python 
import json
lst = [10, 20, 30, 40]
s = json.dumps(lst)
print(s)

Output
[10, 20, 30, 40]

Explanation:

  • json.dumps(lst) converts the Python list lst into a JSON array.
  • The result is a JSON string representation of the list.
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Article Tags:
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