How to use the YAML library in Python

We are going to learn how to use the YAML library in Python. this tutorial on how to work with the YAML format in Python. We use the pyyaml module.

YAML format

YAML (YAML Ain’t Markup Language) is a human-readable data serialization language. YAML natively supports three basic data types: scalars (such as integers, strings, and floats), lists, and associative arrays. YAML is also used in data storage (e.g. debugging output) or transmission (e.g. document headers).

YAML official recommended filename extension for YAML files has been .yaml.

PyYAML

PyYAML is a YAML parser and emitter for Python.

pip install pyyaml

YAML files

#simple.yaml

python : 3
django : 4
wordpress : 6
laravel : 4
php : 7
html : 8

#student.yaml

name:
    - Raj
    - Joi
    - Die
    - Emily
age:
    - 16
    - 21
    - 15
    - 19
cities:
    - Rajkot
    - Morbi
    - Mumbai
    - Surat

Python YAML read

we open the simple.yaml file and load the contents with the yaml.load() method.

#read_yaml.py
#!/usr/bin/env python3

import yaml

with open('simple.yaml') as val:
    data = yaml.load(val, Loader=yaml.FullLoader)
    print(data)

Output:
{'python': 3, 'django': 4, 'wordpress': 6, 'laravel': 4, 'php': 7, 'html': 8}

Python YAML read documents

we open for the student.yaml file and load the contents with the YAML. load_all() method.

#read_documents.py
#!/usr/bin/env python3

import yaml

with open('student.yaml') as val:
    document = yaml.load_all(val, Loader=yaml.FullLoader)
    for value in document:
        for key, vals in value.items():
            print(key, "==>", vals)

Output:
name ==> ['Raj', 'Joi', 'Die', 'Emily']
age ==> [16, 21, 15, 19]
cities ==> ['Rajkot', 'Morbi', 'Mumbai', 'Surat']

Python YAML dump

Python YAML dump() method serializes a Python object into a YAML stream.

#dump.py
#!/usr/bin/env python3

import yaml

users_data = [{'name': 'John', 'city': 'Rajkot'}, {'name': 'Emily', 'city': 'Mumbai'}]

print(yaml.dump(users_data))

Output:
- city: Rajkot
  name: John
- city: Mumbai
  name: Emily

Python YAML write

We write the data with the dump() method.

#write.py
#!/usr/bin/env python3

import yaml

users_data = [{'name': 'John', 'city': 'Rajkot'}, {'name': 'Emily', 'city': 'Mumbai'}]

with open('data.yaml', 'w') as val:
    yaml.dump(users_data, val)

Output:

# data.yaml
- city: Rajkot
  name: John
- city: Mumbai
  name: Emily

Python YAML sorting keys

The example reads data from the items.yaml file and sorts the data by keys in the YAML output.
We can sort keys with the dump’s sort_keys parameter.

#sort_keys.py
#!/usr/bin/env python3

import yaml

with open('data.yaml') as val:
    student_data = yaml.load(val, Loader=yaml.FullLoader)
    print(student_data)

    sorted_data = yaml.dump(student_data, sort_keys=True)
    print(sorted_data)

Output:

[{'city': 'Rajkot', 'name': 'John'}, {'city': 'Mumbai', 'name': 'Emily'}]
- city: Rajkot
  name: John
- city: Mumbai
  name: Emily