api: Add params_show.

content/docs/api-reference/params_show.md

@@ -0,0 +1,253 @@
+# dvc.api.params_show()
+
+Returns all the <abbr>params</abbr> associated with the given <abbr>DVC
+repository</abbr>.
+
+```py
+def params_show(
+    *targets: str,
+    repo: Optional[str] = None,
+    stages: Optional[Union[str, Iterable[str]]] = None,
+    rev: Optional[str] = None,
+    deps: bool = False,
+) -> Dict:
+```
+
+#### Usage:
+
+```py
+import dvc.api
+
+params = dvc.api.params_show()
+```
+
+## Description
+
+Retrieves the <abbr>params</abbr> tracked in a <abbr>DVC repository</abbr>.
+
+Without arguments, this function will retrieve all <abbr>params</abbr> from all
+parameter files, for the current revision.
+
+See the options bellow to restrict the <abbr>params</abbr> retrieved.
+
+## Parameters
+
+- **`*targets`** (str, optional): Names of the parameter files to retrieve
+  <abbr>params</abbr> from. If no `targets` are provided, all parameter files
+  will be used. Note that targets don't necessarily have to be defined in
+  `dvc.yaml`
+
+- **`repo`** (str, optional): location of the <abbr>DVC repository</abbr>.
+  Defaults to the current project (found by walking up from thecurrent working
+  directory tree). It can be a URL or a file system path. Both HTTP and SSH
+  protocols are supported for online Git repos (e.g. [user@]server:project.git).
+
+- **`stages`** (Union[str, Iterable[str]], optional): Name(s) of the stages to
+  retrieve <abbr>params</abbr> from. Defaults to `None`. If no stages are
+  provided, all parameters from all stages will be retrieved.
+
+- **`rev`**: (str, optional): Name of the `Git revision`\_ to retrieve
+  <abbr>params</abbr> from. Example of git revision can be a branch or tag name,
+  a commit hash or a dvc experiment name. Defaults to `HEAD`. If `repo` is not a
+  Git repo, this option is ignored.
+
+- **`deps`**: (bool, optional): Whether to retrieve only <abbr>params</abbr>
+  that are <abbr>stage</abbr> dependencies or not. Defaults to `False`.
+
+## Example: No arguments.
+
+> Working on https://github.com/iterative/example-get-started
+
+```py
+import json
+import dvc.api
+params = dvc.api.get_params()
+print(json.dumps(params, indent=4))
+```
+
+```json
+{
+  "prepare": {
+    "split": 0.2,
+    "seed": 20170428
+  },
+  "featurize": {
+    "max_features": 200,
+    "ngrams": 2
+  },
+  "train": {
+    "seed": 20170428,
+    "n_est": 50,
+    "min_split": 0.01
+  }
+}
+```
+
+## Example: Filtering with `stages`.
+
+> Working on https://github.com/iterative/example-get-started
+
+`stages` can a single string:
+
+```py
+import json
+import dvc.api
+params = dvc.api.get_params(stages="prepare")
+print(json.dumps(params, indent=4))
+```
+
+```json
+{
+  "prepare": {
+    "split": 0.2,
+    "seed": 20170428
+  }
+}
+```
+
+Or an iterable of strings:
+
+```py
+import json
+import dvc.api
+params = dvc.api.get_params(stages=["prepare", "train"])
+print(json.dumps(params, indent=4))
+```
+
+```json
+{
+  "prepare": {
+    "split": 0.2,
+    "seed": 20170428
+  },
+  "train": {
+    "seed": 20170428,
+    "n_est": 50,
+    "min_split": 0.01
+  }
+}
+```
+
+## Example: Using `rev`.
+
+> Working on https://github.com/iterative/example-get-started
+
+```py
+import json
+import dvc.api
+params = dvc.api.get_params(rev="tune-hyperparams")
+print(json.dumps(params, indent=4))
+```
+
+```json
+{
+  "prepare": {
+    "split": 0.2,
+    "seed": 20170428
+  },
+  "featurize": {
+    "max_features": 200,
+    "ngrams": 2
+  },
+  "train": {
+    "seed": 20170428,
+    "n_est": 100,
+    "min_split": 8
+  }
+}
+```
+
+## Example: Using `targets`.
+
+> Working on `multi-params-files` folder of
+> https://github.com/iterative/pipeline-conifguration
+
+You can pass a single target:
+
+```py
+import json
+import dvc.api
+params = dvc.api.params_show(
+  "params.yaml")
+print(json.dumps(params, indent=4))
+```
+
+```json
+{
+  "run_mode": "prod",
+  "configs": {
+    "dev": "configs/params_dev.yaml",
+    "test": "configs/params_test.yaml",
+    "prod": "configs/params_prod.yaml"
+  },
+  "evaluate": {
+    "dataset": "micro",
+    "size": 5000,
+    "metrics": ["f1", "roc-auc"],
+    "metrics_file": "reports/metrics.json",
+    "plots_cm": "reports/plot_confusion_matrix.png"
+  }
+}
+```
+
+Or multiple targets:
+
+```py
+import json
+import dvc.api
+params = dvc.api.params_show(
+  "configs/params_dev.yaml", "configs/params_prod.yaml")
+print(json.dumps(params, indent=4))
+```
+
+```json
+{
+  "configs/params_prod.yaml:run_mode": "prod",
+  "configs/params_prod.yaml:config_file": "configs/params_prod.yaml",
+  "configs/params_prod.yaml:data_load": {
+    "dataset": "large",
+    "sampling": {
+      "enable": true,
+      "size": 50000
+    }
+  },
+  "configs/params_prod.yaml:train": {
+    "epochs": 1000
+  },
+  "configs/params_dev.yaml:run_mode": "dev",
+  "configs/params_dev.yaml:config_file": "configs/params_dev.yaml",
+  "configs/params_dev.yaml:data_load": {
+    "dataset": "development",
+    "sampling": {
+      "enable": true,
+      "size": 1000
+    }
+  },
+  "configs/params_dev.yaml:train": {
+    "epochs": 10
+  }
+}
+```
+
+## Example: Git URL as `repo`.
+
+```py
+import json
+import dvc.api
+params = dvc.api.get_params(
+    repo="https://github.com/iterative/demo-fashion-mnist")
+print(json.dumps(params, indent=4))
+```
+
+```json
+{
+  "train": {
+    "batch_size": 128,
+    "hidden_units": 64,
+    "dropout": 0.4,
+    "num_epochs": 10,
+    "lr": 0.001,
+    "conv_activation": "relu"
+  }
+}
+```

content/docs/command-reference/params/index.md

@@ -112,14 +112,12 @@ $ dvc stage add -n train -d train.py -d users.csv -o model.pkl \
 > Python parameters files.
 
 The `train.py` script will have some code to parse and load the needed
-parameters. For example:
+parameters. For example, you can use `dvc.api.params_show()`:
 
 ```py
-from ruamel.yaml import YAML
+import dvc.api
 
-with open("params.yaml", 'r') as fd:
-    yaml = YAML()
-    params = yaml.load(fd)
+params = dvc.api.params_show()
 
 lr = params['lr']
 epochs = params['train']['epochs']

content/docs/command-reference/run.md

@@ -424,14 +424,12 @@ $ dvc run -n train \
           python train_model.py 20200105 model.p
 ```
 
-`train_model.py` will include some code to open and parse the parameters:
+`train_model.py` can use the `dvc.api.params_show()` to parse the parameters:
 
 ```py
-from ruamel.yaml import YAML
+import dvc.api
 
-with open("params.yaml", 'r') as fd:
-    yaml = YAML()
-    params = yaml.load(fd)
+params = dvc.api.params_show()
 
 seed = params['seed']
 lr = params['train']['lr']

content/docs/command-reference/stage/add.md

@@ -406,14 +406,12 @@ $ dvc stage add -n train \
                 python train_model.py 20200105 model.p
 ```
 
-`train_model.py` will include some code to open and parse the parameters:
+`train_model.py` can use the `dvc.api.params_show()` to parse the parameters:
 
 ```py
-from ruamel.yaml import YAML
+import dvc.api
 
-with open("params.yaml", 'r') as fd:
-    yaml = YAML()
-    params = yaml.load(fd)
+params = dvc.api.params_show()
 
 seed = params['seed']
 lr = params['train']['lr']

content/docs/sidebar.json

@@ -488,6 +488,10 @@
     "label": "Python API Reference",
     "source": "api-reference/index.md",
     "children": [
+      {
+        "slug": "params_show",
+        "label": "params_show()"
+      },
       {
         "slug": "get_url",
         "label": "get_url()"