List of tags

Instantiate an object

Yaml syntax

Use the !obj tag

array:
    !obj numpy.array: { object: [1, 2, 3, 4] }

You can also define its parameters in another file:

array:
    !obj numpy.array: !include "path/to/params.yaml"

params.yaml:

object: [1, 2, 3, 4]

Use it in python

Use the following code to instantiate the object

my_array = conf.array()

If all arguments are not given in the configuration file or you want to overwrite some of them:

my_object = conf.object(
    arg1=1,
    arg2="value"
)

Instantiate a list of objects

Yaml syntax

Use the !obj tag in a list.

list_of_arrays:
    - !obj numpy.array: { object: [1, 2, 3, 4] }
    - !obj numpy.array: { object: [2, 3, 4, 5] }

Use it in python

first_array = conf.list_of_arrays[0]() # Instantiate only the first object
first_object = conf.list_of_objects[0](
    arg1=1,
    arg2="value"
) # Instantiate only the first object of a list of objects with arguments not defined in conf

all_instantiated_arrays = conf.list_of_arrays() # Instantiate all objects in a list
all_instantiated_objects = conf.list_of_objects(
    args1=1,
    arg2="value"
) # Instantiate all objects of a list of objects with arguments not defined in conf

Reference to a class

Yaml syntax

If you want to store a class without instantiating it, use the !class tag

my_class: !class numpy.array

Use it in python

Use the reference just as the node it refers to.

Include another config file

Yaml syntax

Use the !include tag

included_conf: !include "path/to/conf.yaml"

The path can be absolute or relative to the current configuration file.

Use it in python

Use the included config just as if you had copy/paste the content of the included config in the node.

For example, assuming a`=1 is defined in `conf.yaml:

a = conf.included_conf.a()

Import another configuration file

Yaml syntax

Use the !from tag in association with the !include tag. !from will get all includes, merge them and put the result in the current node.

imported_conf:
    !from :
        - !include "path/to/conf1.yaml"
        - !include "path/to/conf2.yaml"
        - !include "path/to/conf3.yaml"
    b: 2

If the variable is defined in multiple files, the highest priority is given to the last included one (here the conf3.yaml file).

If the variable is defined after the !from tag (at the same level), it will overwrite the value defined in included file.

For example, here the value of b will be 2 whatever the value of b is in conf1.yaml, conf2.yaml or conf3.yaml.

Use it in python

Assuming:

conf1.yaml:

a: 1

conf2.yaml:

a: 2
b: 1

conf3.yaml:

c: 2

a = conf.imported_conf.a() # is equal to 2 because conf2.yaml has the priority on conf1.yaml
b = conf.imported_conf.b() # is equal to 2 because it is overwritten
c = conf.imported_conf.c() # is equal to 2

Get the value of an env variable

Yaml syntax

You can recover the value of an environment variable using the !env tag.

my_env_var: !env ENV_VARIABLE

Use it in python

my_env_var = conf.my_env_var()

Format a string

Yaml syntax

Use the !f tag (such as in python).

string: !f "Hi $USER !"

Where $USER is an environment variable.

Use it in python

my_string = conf.string() # is equal to "Hi root !" if $USER = "root"

Refer to another variable

Yaml syntax

Use the !ref tag

experiment:
    training:
        batch_size: 100

    relative_ref_to_batch_size: !ref training/batch_size # 100
    absolute_ref_to_batch_size: !ref /experiment/training/batch_size # 100
    relative_ref_to_cpu: ../resources/cpu # 2

resources:
    cpu: 2

Use it in python

batch_size = conf.experiment.relative_ref_to_batch_size() # is equal to 100
batch_size = conf.experiment.absolute_ref_to_batch_size() # is equal to 100
batch_size = conf.experiment.relative_ref_to_cpu() # is equal to 2