Object created with pyyaml doesn't have some attributes

Question

I want to create an object with PyYAML. Consider the following code:

import yaml

doc = """
- !!python/object:__main__.Person {name: abc}
"""

class Person(object):
    def __init__(self, name):
        self.name = name
        self.age = 26

data = yaml.load(doc)
p = data[0]
print(dir(p))

The output of the above code is:

[__class__,__delattr__,__dict__,__dir__,__doc__,__eq__,__format__,__ge__,__getattribute__,__gt__,__hash__,__init__,__le__,__lt__,__module__,__ne__,__new__,__reduce__,__reduce_ex__,__repr__,__setattr__,__sizeof__,__slotnames__,__str__,__subclasshook__,__weakref__,name]

As you can see, my object does not have 'age' attribute! Therefor calling

print(p.age)

would generate an error.

How can I fix this problem? I know that I can use

doc = """
- !!python/object:__main__.Person {name: abc, age: 26}
"""

but it doesn't make sense to me because a class might have hundreds of internal attributes. It would be impossible to create such an object like this.

Answer 1

I found the solution (thanks to @asherbar 's comment):

import yaml

doc = """
- !Person {name: abc}
"""

def yamlobj(tag):
    def wrapper(cls):
        def constructor(loader, node):
            fields = loader.construct_mapping(node)
            return cls(**fields)
        yaml.add_constructor(tag, constructor)
        return cls
    return wrapper

@yamlobj('!Person')
class Person(object):
    def __init__(self, name):
        self.name = name
        self.age = 26

data = yaml.load(doc)
p = data[0]
print(dir(p))