yachain

YAML access on chained attribute names.

Install

$ pip install yachain

Suppose we have:

---
# config
network:
   name: developers
   gitserver:
      ip: 192.168.178.101
      netmask: 255.255.255.0
      gateway: 192.168.178.1
      packages:
      - yum
      - gcc

With yachain we can access this as:

>>> import yachain

>>> c = yachain.Config().load("netw.cfg")
>>> print(c["network::gitserver::gateway"])
192.168.178.1
>>> print(c["network::gitserver::packages"])
['yum', 'gcc']

References to files / paths independent from environment

References to files and paths can be used relative and absolute. In case an attribute ends on path or file then the path can be prefixed automatically when operation from a virtual environment is detected. The works by default upper and lower case and can be overriden.

Using the prefix makes it possible to use the same config in different environments.

import yachain
import yaml
import sys
import os

# yaml config:
yc = """
---
app:
  logfile: var/log/app.log
  textrules: var/app.app.txt
  database_path: var/app/db
  database_file: /var/app/db/db.txt
  database_name: db.txt
"""

PREFIX = "/" if not hasattr(sys, 'real_prefix') else sys.prefix
# CONFIG_FILE = os.path.join(PREFIX, "etc/app/app.cfg")
config = yachain.Config(prefix=PREFIX, configdata=yaml.load(yc))


for A in ["logfile",
          "textrules",
          "database_path",
          "database_file",
          "database_name"]:
    k = "app::{}".format(A)
    print config[k]

When run from a virtual environment, this will give us:

/home/user/venv/var/log/app.log
var/app.app.txt
/home/user/venv/var/app/db
/var/app/db/db.txt
db.txt

So, as expected, the logfile and database_path got the PREFIX.

When run from a non-virtual environment, this will give us:

/var/log/app.log
var/app.app.txt
/var/app/db
/var/app/db/db.txt
db.txt

So, as expected, prefixed with "/".