Merge branch 'f-casting-transformers' into 'dev'

New transformer functions for casting types of variables

See merge request !203

CHANGELOG.md

@@ -19,7 +19,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - ZipFileConverter that opens zip files and exposes their contents as
   File and Directory structure elements.
 - `linkahead-crawler` script as alias for `caosdb-crawler`.
-- Transformer function definietion in the cfood support variable
+- New transformers of the form `cast_to_*` which allow casting
+  variables to `int`, `float`, `str` and `bool`.
+- Transformer function definition in the cfood support variable
   substitutions now.
 
 ### Changed ###

src/caoscrawler/default_transformers.yml

@@ -15,3 +15,15 @@ date_parse:
 datetime_parse:
   package: caoscrawler.transformer_functions
   function: datetime_parse
+cast_to_int:
+  package: caoscrawler.transformer_functions
+  function: cast_to_int
+cast_to_float:
+  package: caoscrawler.transformer_functions
+  function: cast_to_float
+cast_to_bool:
+  package: caoscrawler.transformer_functions
+  function: cast_to_bool
+cast_to_str:
+  package: caoscrawler.transformer_functions
+  function: cast_to_str

src/caoscrawler/transformer_functions.py

@@ -99,3 +99,56 @@ Parameters
     fmt = params.get("datetime_format", fmt_default)
     dt_str = datetime.datetime.strptime(in_value, fmt).strftime(fmt_default)
     return dt_str
+
+
+def cast_to_int(in_value: Any, params: dict) -> int:
+    """
+    Cast the `in_value` to int.
+
+    Parameters
+    ==========
+    No parameters.
+    """
+    return int(in_value)
+
+
+def cast_to_float(in_value: Any, params: dict) -> float:
+    """
+    Cast the `in_value` to float.
+
+    Parameters
+    ==========
+    No parameters.
+    """
+    return float(in_value)
+
+
+def cast_to_bool(in_value: Any, params: dict) -> bool:
+    """
+    Cast the `in_value` to bool.
+
+    This is done by comparing `in_value` to "True".
+    Only "true", "True", "False" and "false" are accepted as possible values.
+    All other input values raise an error.
+
+    Parameters
+    ==========
+    No parameters.
+    """
+    val = str(in_value).lower()
+    if val == "true":
+        return True
+    if val == "false":
+        return False
+    raise ValueError("Invalid value for type cast to bool: {}".format(in_value))
+
+
+def cast_to_str(in_value: Any, params: dict) -> str:
+    """
+    Cast the `in_value` to str.
+
+    Parameters
+    ==========
+    No parameters.
+    """
+    return str(in_value)

unittests/test_transformers.py

@@ -36,7 +36,9 @@ import pytest
 from caoscrawler.converters import Converter, ListElementConverter
 from caoscrawler.scanner import create_transformer_registry, scan_directory
 from caoscrawler.stores import GeneralStore
-from caoscrawler.transformer_functions import replace
+from caoscrawler.transformer_functions import (cast_to_bool, cast_to_float,
+                                               cast_to_int, cast_to_str,
+                                               replace, split)
 from pytest import raises
 
 UNITTESTDIR = Path(__file__).parent
@@ -162,6 +164,38 @@ def test_empty_functions_list(converter_registry):
     assert values['b'] == "16_45"
 
 
+def test_cast_transformer_functions():
+    for val in ("True", "true", "False", "false"):
+        assert type(cast_to_bool(val, {})) == bool
+        if val[1] == "r":
+            assert cast_to_bool(val, {}) is True
+        else:
+            assert cast_to_bool(val, {}) is False
+    for val_err in ("jaksdlfj", "0", 1):
+        with pytest.raises(ValueError):
+            cast_to_bool(val_err, {})
+    assert cast_to_bool(False, {}) is False
+    assert cast_to_bool(True, {}) is True
+
+    assert cast_to_int("24", {}) == 24
+    assert cast_to_int(24.0, {}) == 24
+    assert cast_to_int(24, {}) == 24
+    assert cast_to_int("-24", {}) == -24
+    with pytest.raises(ValueError):
+        cast_to_int("24dsf", {})
+    with pytest.raises(ValueError):
+        cast_to_int("24.0", {}) == 24
+
+    assert cast_to_float("24", {}) == 24.0
+    assert cast_to_float("24.0", {}) == 24.0
+    assert cast_to_float(24.0, {}) == 24.0
+    assert cast_to_float(24, {}) == 24.0
+    with pytest.raises(ValueError):
+        cast_to_float("24dsf", {})
+
+    assert cast_to_str(24, {}) == "24"
+
+
 def test_replace_variables():
     vals = GeneralStore()
     vals["test"] = "with"