yaml_configuration_file_in_python

yaml_python_config_file

'''
In this example I will show you how to read and write yaml configuration files in python
(this is built for python 3.6, you can copy this into a Jupyter notebook and execute!)

Background Information:
-----------------------
yaml is a configuration language:
- see this link for a good introduction on what is possible with yaml: https://learnxinyminutes.com/docs/yaml/

In python you need pyyaml to write and read yaml files:
- install with: pip install pyyaml
- see this link for the documentation: http://pyyaml.org/wiki/PyYAMLDocumentation
'''

# Step1: import the library
# ------------------------------------------------------
import yaml

# Step 2: Read the Configuration file
# ------------------------------------------------------
# - you can read yaml into a Python Class: that way you can make sure you get, what you expect
# - normally you will read from file 
# - here we will also read from a string, so that you better see how the yaml file should look

# make a configuration class, this here is the configuration of a wordpress xml parser

class Configuration(yaml.YAMLObject):
    yaml_tag = u'!Config'
    def __init__(self, channel_info, post_types, status_types):
        self.channel_info = channel_info
        self.post_types = post_types
        self.status_types = status_types

    def __repr__(self):
        return "Configuration for {}".format(str(self.channel_info))

# now you can read from a configuration file directly into the class 

with open("config.yml", 'r') as ymlfile:
    cfg = yaml.load(ymlfile)   
    
    # make sure you got the correct structure
    
    if not isinstance(cfg, Configuration):
        raise SyntaxError("{} is not a valid configuration file".format(ymlfile.name))

# you can also read from a string:
config = """
!Config
channel_info: [title, 'wp:base_site_url', description, language]
post_types: [attachement, post, page] 
status_types: [draft, publish] 
"""

cfg = yaml.load(config)  
print(cfg)
    
# make sure you got the correct structure

if not isinstance(cfg, Configuration):
    raise SyntaxError("{} is not a valid configuration file".format(ymlfile.name))

# Step 3: Write a configuration file
# ------------------------------------------------------
# - you can reverse this procedure and write a configuration file from a python class

with open("config_out.yml", 'w') as ymlfile:
    ymlfile.write(yaml.dump(cfg))