How can I parse a YAML file in Python

Question

How can I parse a YAML file in Python?

Answer 1

The easiest and purest method without relying on C headers is PyYaml (documentation), which can be installed via pip install pyyaml:

#!/usr/bin/env python  import yaml  with open("example.yaml", "r") as stream:     try:         print(yaml.safe_load(stream))     except yaml.YAMLError as exc:         print(exc) 

And that's it. A plain yaml.load() function also exists, but yaml.safe_load() should always be preferred unless you explicitly need the arbitrary object serialization/deserialization provided in order to avoid introducing the possibility for arbitrary code execution.

Note the PyYaml project supports versions up through the YAML 1.1 specification. If YAML 1.2 specification support is needed, see ruamel.yaml as noted in this answer.

Also, you could also use a drop in replacement for pyyaml, that keeps your yaml file ordered the same way you had it, called oyaml. View synk of oyaml here

Answer 2

Read & Write YAML files with Python 2+3 (and unicode)

# -*- coding: utf-8 -*- import yaml import io  # Define data data = {     'a list': [         1,          42,          3.141,          1337,          'help',          u'€'     ],     'a string': 'bla',     'another dict': {         'foo': 'bar',         'key': 'value',         'the answer': 42     } }  # Write YAML file with io.open('data.yaml', 'w', encoding='utf8') as outfile:     yaml.dump(data, outfile, default_flow_style=False, allow_unicode=True)  # Read YAML file with open("data.yaml", 'r') as stream:     data_loaded = yaml.safe_load(stream)  print(data == data_loaded) 

Created YAML file

a list: - 1 - 42 - 3.141 - 1337 - help - € a string: bla another dict:   foo: bar   key: value   the answer: 42 

Common file endings

.yml and .yaml

Alternatives

• CSV: Super simple format (read & write)
• JSON: Nice for writing human-readable data; VERY commonly used (read & write)
• YAML: YAML is a superset of JSON, but easier to read (read & write, comparison of JSON and YAML)
• pickle: A Python serialization format (read & write)
• MessagePack (Python package): More compact representation (read & write)
• HDF5 (Python package): Nice for matrices (read & write)
• XML: exists too *sigh* (read & write)

For your application, the following might be important:

• Support by other programming languages
• Reading / writing performance
• Compactness (file size)

See also: Comparison of data serialization formats

In case you are rather looking for a way to make configuration files, you might want to read my short article Configuration files in Python