yacs的使用小记

【build your own config】

https://github.com/rentainhe/config-builder/blob/master/notes/yacs-notes.md
​github.com/rentainhe/config-builder/blob/master/notes/yacs-notes.md
yacs库，用于为一个系统构建config文件

Install
$ pip install yacs
Import
from yacs.config import CfgNode as CN
Usage
create config node
需要创建CN()这个作为容器来装载我们的参数，这个容器可以嵌套

from yacs.config import CfgNode as CN
__C = CN()
__C.name = ‘test’
__C.model = CN() # 嵌套使用
__C.model.backbone = ‘resnet’
__C.model.depth = 18

print(__C)
‘’’
name: test
model:
backbone: resnet
depth: 18
‘’’
API reference
use __C as created config file

1. clone()
   return a copy config file, so the defaults will not be altered

def get_cfg_defaults():
return __C.clone()
2. clear()
clear your config file, you will get None as the result

print(__C.clear()) # None
3. merge_from_file()
对于不同的实验，你有不同的超参设置，所以你可以使用yaml文件来管理不同的configs，然后使用merge_from_file()这个方法，这个会比较每个experiments特有的config和默认参数的区别，会将默认参数与特定参数不同的部分，用特定参数覆盖。

__C.merge_from_file(“./test_config.yaml”)
Addition:

你需要merge的yaml文件中，不能有default参数中不存在的参数，不然会报错，但是可以比default中设定的参数少，比如default文件中有name参数，这是不需要特定改动的，你可以在yaml中不设置name这个key。
from yacs.config import CfgNode as CN

default cfgs

__C = CN()
__C.name = ‘test’
__C.model = CN()
__C.model.backbone = ‘resnet’
__C.model.depth = 18

yaml cfgs

不报错的情况1：参数和default中一样多，并且层级关系一致

name: test
model:
backbone: resnet
depth: 18

不报错的情况2：参数可以比default中少，以下例子就不包含name和model.backbone

model:
depth: 34

报错的情况1：以下多了model.batch_normalization这个额外的key，这在default中是不存在的

name: test
model:
backbone: resnet
depth: 29
batch_normalization: True

报错的情况2：关键词不一致，这里的关键词是na_me，而default中是name

na_me: test
4. merge_from_list()
可以用list来传递参数

from yacs.config import CfgNode as CN
__C = CN()
__C.name = ‘test’
__C.model = CN()
__C.model.backbone = ‘resnet’
__C.model.depth = 18
print(__C)
‘’’
model:
backbone: resnet
depth: 18
name: test
‘’’

opts = [“name”, ‘test_name’, “model.backbone”, “vgg”]
__C.merge_from_list(opts)
print(__C)
‘’’
model:
backbone: vgg
depth: 18
name: test_name
‘’’
other details are the same as merge_from_file

5. merge_from_other_cfg()
   the same as merge_from_file and merge_from_list, the only difference is that the merged file is also a CfgNode class

6. freeze()
   freeze the configs, and you can not change the value after this operation

from yacs.config import CfgNode as CN
__C = CN()
__C.name = ‘test’
__C.model = CN()
__C.model.backbone = ‘resnet’
__C.model.depth = 18

freeze the config

__C.freeze()

try to change the name’s value, raise an error

__C.name = ‘test2’ # error
7. defrost()
reverse operation of freeze()

from yacs.config import CfgNode as CN
__C = CN()
__C.name = ‘test’
__C.model = CN()
__C.model.backbone = ‘resnet’
__C.model.depth = 18

freeze the config

__C.freeze()

try to change the name’s value, raise an error

__C.name = ‘test2’ # error

__C.defrost() # not freeze cfgs, after this operation you can change the value
__C.name = ‘test2’ # work