How can I do string concatenation, or string replacement in YAML?

Question

I have this:

user_dir: /home/user
user_pics: /home/user/pics

How could I use the user_dir for user_pics? If I have to specify

Answer 1

string.join() won't work in Python3, but you can define a !join like this:

import functools
import yaml

class StringConcatinator(yaml.YAMLObject):
    yaml_loader = yaml.SafeLoader
    yaml_tag = '!join'
    @classmethod
    def from_yaml(cls, loader, node):
        return functools.reduce(lambda a, b: a.value + b.value, node.value)

c=yaml.safe_load('''
user_dir: &user_dir /home/user
user_pics: !join [*user_dir, /pics]''')
print(c)