# YAML to JSON in Python: a five-line script and the traps to avoid

> PyYAML reads it, the json module writes it, and quoting fixes most of the surprises.

URL: https://claudegpt.si/news/yaml-to-json-python-script  
Published: 2026-10-27T15:08:01.777Z  
Author: ClaudeGPT Si Newsroom  
Section: Guides  
Topics: Python, YAML, JSON  
Publisher: ClaudeGPT Si

## Key takeaways

- Load YAML with yaml.safe_load and write it with json.dumps; pass default=str so dates do not crash the dump.
- PyYAML follows YAML 1.1, so unquoted yes, no, on and off become booleans in the JSON.
- For one-off files, AyeTab converts YAML to JSON free in the browser without uploading the file.

To convert YAML to JSON in Python, load the file with PyYAML's `yaml.safe_load` and write the result with the standard `json` module. That takes about five lines. For a single file you only need to look at once, the free [AyeTab converter](https://app.ayetab.com/tools/yaml-json) does the same job in a browser tab with no code and no upload.

## The script

Install PyYAML first:

```bash
pip install pyyaml
```

Then:

```python
import json
import sys

import yaml

with open(sys.argv[1]) as f:
    data = yaml.safe_load(f)

print(json.dumps(data, indent=2, default=str))
```

Run it as `python yaml2json.py config.yaml > config.json`. The `indent=2` gives readable output; drop it when the JSON goes into a request body and size matters. Keys keep the order they had in the YAML file, since Python dicts preserve insertion order.

## Why `safe_load` and not `load`

PyYAML's own README tells you to use `yaml.safe_load` when you do not trust the input. The plain loader can build arbitrary Python objects from tags inside the file, which is not something you want from a config file that came out of a ticket, a vendor or a pull request. `safe_load` sticks to plain types: dicts, lists, strings, numbers, booleans and null, which map cleanly onto JSON.

## Three traps, and the fix for each

| Trap | What happens | Fix |
| --- | --- | --- |
| Dates | An unquoted date loads as a Python date, and `json.dumps` raises a TypeError | Pass `default=str`, or quote dates in the YAML |
| Plain words as booleans | PyYAML parses YAML 1.1, where `yes`, `no`, `on` and `off` become true or false | Quote those values in the source file |
| Several documents in one file | `safe_load` expects one document and complains at the `---` | Use `yaml.safe_load_all` and dump a list |

The boolean one causes the most confusion in operations work. A feature flag file with `enabled: on`, or a list of country codes that includes `NO`, will not come out the way it reads. If you need YAML 1.2 behaviour, where only `true` and `false` count, use a parser that implements 1.2 instead.

For multi-document files such as Kubernetes manifests, the change is small:

```python
docs = list(yaml.safe_load_all(f))
print(json.dumps(docs, indent=2, default=str))
```

## Writing the output to a file

Printing to standard output keeps the script composable, but some teams prefer the script to write next to the source. Swap the last line for:

```python
from pathlib import Path

out = Path(sys.argv[1]).with_suffix(".json")
out.write_text(json.dumps(data, indent=2, default=str))
```

Add `ensure_ascii=False` to `json.dumps` if the YAML holds accented names or other non-ASCII text and you want them written as is rather than as escape sequences.

## When not to write Python at all

A script makes sense when the conversion repeats: a build step, a CI check, a migration across hundreds of files. For anything shorter there are faster routes.

- **Command line.** yq, a single Go binary, converts with `yq -o json file.yaml` and fits into shell pipelines.
- **Browser.** AyeTab gives you a YAML pane and a JSON pane, converts both ways, and copies the result with one click. It is free, needs no account, and parses everything locally, so an internal config file stays on your machine. Once the page loads it works offline too.

The Python route still wins when you need to change the data on the way through, such as filtering keys, merging files or checking values, since you already have the parsed dict in hand.

## Keep the quick version close

If you convert files a few times a week, the [AyeTab Chrome extension](https://ayetab.com) puts the same converter, and the rest of its developer tools, on your new tab and in a side panel. Ctrl+K or Cmd+K opens a command palette that finds the tool by name.

## FAQ

**Which Python library converts YAML to JSON?**
PyYAML reads the YAML and the built-in `json` module writes JSON. Use `yaml.safe_load` for files you did not write.

**How do I convert a YAML file with several documents?**
Use `yaml.safe_load_all`, collect the documents into a list and dump that list as a JSON array.

**Can I convert YAML to JSON without Python?**
Yes. Use yq on the command line, or paste the file into AyeTab's free browser converter.

## Frequently asked questions

### Which Python library converts YAML to JSON?

PyYAML reads the YAML and the built-in json module writes JSON. Use yaml.safe_load for files you did not write.

### How do I convert a YAML file with several documents?

Use yaml.safe_load_all, collect the documents into a list and dump that list as a JSON array.

### Can I convert YAML to JSON without Python?

Yes. Use yq on the command line, or paste the file into AyeTab's free browser converter.

## Sources

- [PyYAML](https://github.com/yaml/pyyaml), GitHub
- [PyYAML on PyPI](https://pypi.org/project/PyYAML/), PyPI
- [Boolean type for YAML 1.1](https://yaml.org/type/bool.html), yaml.org
- [yq](https://github.com/mikefarah/yq), GitHub
- [YAML to JSON Converter Online: Free](https://app.ayetab.com/tools/yaml-json), AyeTab
- [AyeTab](https://ayetab.com), AyeTab