pyyaml¶

The canonical YAML library for Python, powering Ansible and the Python ecosystem.

Overview¶

pyyaml is the standard YAML library for Python. It's the foundation of Ansible, the world's most popular automation tool, and countless Python applications.

Repository: github.com/yaml/pyyaml
Language: Python (with C extension via libyaml)
License: MIT
Maintainer: YAML LLC

Why pyyaml Matters¶

Powers Automation¶

pyyaml is the YAML engine behind:

Ansible - The world's leading automation platform
Salt - Configuration management and orchestration
Home Assistant - Smart home automation
AWS CloudFormation - Infrastructure-as-code
Pre-commit - Multi-language git hook framework
Countless Python applications and frameworks

Massive Adoption¶

300M+ downloads per month via PyPI
De facto standard for YAML in Python
Used by millions of Python developers
Essential infrastructure for DevOps and automation

Battle-Tested¶

Decades of production use
Proven reliability at scale
Extensive compatibility
Active community

YAML LLC Maintenance¶

Under YAML LLC's stewardship, pyyaml receives:

Security First¶

Regular security audits
Rapid vulnerability patching
Safe defaults (SafeLoader)
YES members get 48-hour early CVE notifications

Active Development¶

Python 3.x compatibility improvements
Performance optimizations via libyaml
Bug fixes and stability improvements
Documentation enhancements

Professional Support¶

Responsive to issues and pull requests
Clear development roadmap
Integration support for enterprise users
Backwards compatibility focus

Maintenance & Accountability¶

pyyaml is professionally maintained by YAML LLC, led by Ingy döt Net, co-creator of YAML.

Security contact: security@yaml.com
Disclosure policy: Coordinated disclosure with advance notice to YES members
Release cadence: Security patches prioritized, feature releases quarterly

Need supply chain documentation for compliance? Learn about the YES Program →

Technical Details¶

Features¶

Full YAML 1.1 support (YAML 1.2 in development)
Pure Python and C-accelerated (libyaml) modes
Safe and unsafe loading options
Custom types and constructors
Comprehensive error reporting
Streaming API for large documents

Performance¶

C extension via libyaml for speed
Efficient memory usage
Handles multi-document streams
Optimized for common use cases

API¶

import yaml

# Safe loading (recommended)
with open('config.yaml') as f:
    config = yaml.safe_load(f)

# Dump Python objects to YAML
with open('output.yaml', 'w') as f:
    yaml.dump(data, f)

Use Cases¶

Ansible Playbooks¶

Every Ansible playbook uses pyyaml:

---
- name: Configure web servers
  hosts: webservers
  tasks:
    - name: Install nginx
      apt:
        name: nginx
        state: present

Application Configuration¶

Python applications use pyyaml for configuration:

database:
  host: localhost
  port: 5432
  name: myapp

logging:
  level: INFO
  file: /var/log/app.log

Data Processing¶

Scientists and data engineers use pyyaml:

import yaml

# Load experimental parameters
with open('experiment.yaml') as f:
    params = yaml.safe_load(f)

# Process data using parameters
results = run_experiment(**params)

Security¶

pyyaml provides multiple loaders with different security levels:

Loader	Use Case	Safety
`safe_load()`	Untrusted input	Safe
`full_load()`	Known YAML tags	Use with caution
`unsafe_load()`	Trusted input only	Dangerous

Security Best Practice

Always use yaml.safe_load() for untrusted input. Never use yaml.load() or yaml.unsafe_load() with user-provided data.

Support pyyaml¶

pyyaml is maintained through the YES Program. YES members get:

Priority support for pyyaml issues
Early notification of security vulnerabilities
Influence over roadmap and feature development
Direct access to maintainers

Join the YES Program →