Minor changes

Fixed typos in docs.
Added some text in inline docs.
Added a function in preparation of a feature allowing
variable names to be referenced in an HTML document.

src/dash/htmlayout/builder.py

@@ -1,6 +1,6 @@
 """Build layouts from HTML snippets."""
+import logging
 import re
-import sys
 from importlib import import_module
 from os import PathLike
 from typing import Optional, Type, Any, Union
@@ -11,6 +11,8 @@
 
 from .converters import evaluate
 
+logger = logging.getLogger("dash.htmlayout")
+
 
 class Builder:
     """
@@ -117,10 +119,9 @@ def _autodetect_components(cls):
                             full_name: str = f"{full_prefix}{tag_name}"
                             cls._component_registry[full_name] = symbol
             except ImportError:
-                print(
+                logger.warning(
                     f"Warning: {module_name} is listed in LayoutBuilder "
-                    f"registry but could not be imported.",
-                    file=sys.stderr,
+                    f"registry but could not be imported."
                 )
 
     @classmethod
@@ -131,7 +132,7 @@ def register_library(
         Register a new module providing Dash components.
 
         A sensible default is already provided for known libraries,
-        but you can custom libraries with this method. You just have to
+        but you can register custom libraries with this method. You just have to
         call this by passing a module path and a prefix to apply to detected
         components:
 
@@ -140,6 +141,13 @@ def register_library(
 
         Builder.register_library("dash_colorful_lib", "colorful")
         ```
+
+        You can then insert components in your HTML files with the
+        provided prefix, ie.:
+
+        ```html
+        <colorful-componentname id="component-id">...
+        ```
         """
         if path not in cls._module_registry or replace:
             cls._module_registry[path] = prefix
@@ -165,7 +173,7 @@ def load(self, path: Union[PathLike, str]) -> Component:
 
     def get_component(self, identifier: str) -> Optional[Component]:
         """
-        Get component instance in the loqded lqyout given an ID.
+        Get component instance in the loaded layout given an ID.
 
         Args:
             identifier: id given to the component.

src/dash/htmlayout/converters.py

@@ -11,6 +11,25 @@ def evaluate(string: str) -> Any:
 
     Returns:
         A Python literal.
-
     """
     return literal_eval(string)
+
+
+def evaluate_var(name: str) -> Any:
+    """
+    Get a local variable from its name.
+
+    Args:
+        name: local variable name. Must start with "data_".
+
+    Returns:
+        The content of the variable with the name passed as an argument.
+
+    Raises:
+        KeyError: when you give a non-existing name.
+        ValueError: if the variable name does not start with data_.
+    """
+    if name.startswith("data_"):
+        return locals()[name]
+    else:
+        raise ValueError("Only var names starting with data_ are allowed.")