Edit YAML Files in Python (Multiple Examples)

In this tutorial, you’ll learn how to read, modify, and write YAML files in Python using the ruamel.yaml library.

We’ll start with simple operations like changing scalar values, updating nested structures, manipulating lists, and applying conditional changes.

 

 

Change Scalar Value

To change a scalar value in a YAML file, use ruamel.yaml to load the data, modify the value, and then save it back.

from ruamel.yaml import YAML
yaml = YAML()
with open('config.yaml', 'r') as file:
    data = yaml.load(file)
data['database']['host'] = '192.168.1.10'

# Save the updated YAML file
with open('config.yaml', 'w') as file:
    yaml.dump(data, file)

Output:

Suppose config.yaml initially contains:

database:
  host: localhost
  port: 5432

After running the code, config.yaml will be:

database:
  host: 192.168.1.10
  port: 5432

 

Update Nested Value

To update a nested value, such as a key within a nested dictionary, access it directly and assign a new value.

data['server']['credentials']['username'] = 'Amina'
data['server']['credentials']['password'] = 'securepassword123'
with open('config.yaml', 'w') as file:
    yaml.dump(data, file)

Output:

If config.yaml contains:

server:
  credentials:
    username: admin
    password: adminpass

After running the code, it becomes:

server:
  credentials:
    username: Amina
    password: securepassword123

 

Modify Elements in a List

To modify elements in a list within the YAML data, access the list and change the desired elements.

services = data['services']
services[1] = 'nginx'
with open('config.yaml', 'w') as file:
    yaml.dump(data, file)

Output:

Given config.yaml has:

services:
  - apache
  - mysql
  - redis

After running the code, config.yaml changes to:

services:
  - apache
  - nginx
  - redis

 

Change Values Based on a Condition

To change values based on a condition, loop through the list to find and modify specific entries.

# Update the email of a user named 'Mohamed'
for user in data['users']:
    if user['name'] == 'Mohamed':
        user['email'] = 'mohamed@example.com'
with open('config.yaml', 'w') as file:
    yaml.dump(data, file)

Output:

If config.yaml originally contains:

users:
  - name: Mohamed
    email: mohamed_old@example.com
  - name: Sara
    email: sara@example.com

After executing the code, it updates to:

users:
  - name: Mohamed
    email: mohamed@example.com
  - name: Sara
    email: sara@example.com