json.dumps() in Python

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.

{"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.

{"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.

{
 "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.

{"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.

[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.

Related Articles:

• json.loads()
• Write and parse JSON using Python