Writing and Reading YAML config file in Python

We’ve already covered .ini, .json and .xml in below articles, in this article we’ll focus on .yaml config files.

• .ini file in Python
• .json file in Python
• .xml file in Python

Reading and Writing config data to YAML file in Python

YAML or YAML Ain't Markup Language is a case sensitive and human-friendly data serialization language used mainly for configurations.

For reading and writing to the YAML file, we first need to install the PyYAML package by using the following command.

$ pip install pyyaml

Let’s now dive into read and write operations to the YAML file.

Creating YAML config file in Python

We can write data to the YAML file using yaml.dump() method which takes python object and file pointer as parameters.

In the below example, we are writing the dictionary article_info to the YAML file tutswiki.yaml.

import yaml

article_info = [
    {
        'Details': {
        'domain' : 'www.tutswiki.com',
        'language': 'python',
        'date': '11/09/2020'
        }
    }
]

with open("tutswiki.yaml", 'w') as yamlfile:
    data = yaml.dump(article_info, yamlfile)
    print("Write successful")

Output:

Write successful

Process finished with exit code 0

File: tutswiki.yaml

- Details:
    date: 11/09/2020
    domain: www.tutswiki.com
    language: python

Note: sort_keys parameter in dump() method can be used to sort the keys in ascending order.

sorted = yaml.dump(data, sort_keys = True)

Reading a key from YAML config file

We can read the data using yaml.load() method which takes file pointer and Loader as parameters. FullLoader handles the conversion from YAML scalar values to the Python dictionary.

To read the value from the file, we write the below code

import yaml

with open("tutswiki.yaml", "r") as yamlfile:
    data = yaml.load(yamlfile, Loader=yaml.FullLoader)
    print("Read successful")
print(data)

Output:

Read successful
[{'Details': {'date': '11/09/2020', 'domain': 'www.tutswiki.com', 'language': 'python'}}]

Process finished with exit code 0

Now if we want to read the value of domain, we would write

print(data[0]['Details']['domain'])

The index [0] is used to select the tag we want to read. And we move further using the key values.

Output:

www.tutswiki.com

Updating a key in YAML config file

What if we want to update the language python to java? For that, we will have to first read the file, reach to the key language and update its value and write the data to the file as done below.

import yaml

article_info = [
    {
        'Details': {
        'domain' : 'www.tutswiki.com',
        'language': 'python',
        'date': '11/09/2020'
        }
    }
]

with open("tutswiki.yaml", "r") as yamlfile:
    data = yaml.load(yamlfile, Loader=yaml.FullLoader)
    print(data)
    print("Read successful")
    data[0]['Details']['language'] = 'java'
    print("Value of language updated from 'python' to 'java'")
    yamlfile.close()

with open("tutswiki.yaml", 'w') as yamlfile:
    data1 = yaml.dump(data, yamlfile)
    print(data)
    print("Write successful")
    yamlfile.close()

Output:

[{'Details': {'date': '11/09/2020', 'domain': 'www.tutswiki.com', 'language': 'python'}}]
Read successful
Value of language updated from 'python' to 'java'
[{'Details': {'date': '11/09/2020', 'domain': 'www.tutswiki.com', 'language': 'java'}}]
Write successful

Process finished with exit code 0

File: tutswiki.yaml

- Details:
    date: 11/09/2020
    domain: www.tutswiki.com
    language: java

As you can see, language in tutswiki.yaml file has been updated successfully.