How to load yaml into a python class object with UnsafeLoader

06-19-2023 194 words One minute 0 views

Contents

Here is a pyyaml code snippet that writes a python class object to yaml file and then also loads the yaml file back to python class object.

Warning: Using yaml.UnsafeLoader is not safe and could lead to security issues such as arbitrary code execution.

Source Code

import yaml # pip install pyyaml

# Define a custom class
class PersonClass:
    def __init__(self, name, age, gender):
        self.name = name
        self.age = age
        self.gender =  gender
    
    def __str__(self):
      return repr(self)

# Create an instance of the person class
obj = PersonClass("Jane Doe", 33, "Female")


# Try to serialize the object to YAML
try:
    print(yaml.dump(obj))
    
except yaml.RepresenterError as e:
    print("RepresenterError:", e)

how to load yaml into a python class object with yaml.UnsafeLoader

myobj = yaml.load("""!!python/object:__main__.PersonClass
age: 24
gender: Male
name: John Doe
""", Loader=yaml.UnsafeLoader) # Parse the first YAML document in a stream and produce the corresponding Python object.

# Access the attributes of the object
print(myobj.name)
print(myobj.age)

# Serialize the object back to YAML
print(yaml.dump(myobj))

Potential pyyaml errors

yaml.constructor.ConstructorError: could not determine a constructor for the tag ’tag:yaml.org,2002:python/object:main.PersonClass'

TypeError: load() missing 1 required positional argument: ‘Loader’

About `PyYAML`

PyYAML - A YAML parser and emitter for Python.