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

As of August 2019:

To make Chris' solution work, you actually need to add Loader=yaml.Loader to yaml.load(). Eventually, the code would look like this:

import yaml

## define custom tag handler
def join(loader, node):
    seq = loader.construct_sequence(node)
    return ''.join([str(i) for i in seq])

## register the tag handler
yaml.add_constructor('!join', join)

## using your sample data
yaml.load("""
user_dir: &DIR /home/user
user_pics: !join [*DIR, /pics]
""", Loader=yaml.Loader)

See this GitHub issue for further discussion.