Python implementation

.github/workflows/github-actions.yml

@@ -1,9 +1,14 @@
 name: github-actions
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - "*"
+    tags-ignore:
+      - "v*.*.*"
 env:
   BUILD_IMAGE: bedasoftware/fhirpath-extract:main
 jobs:
-  Build:
+  build-and-test-fpml-server-ts:
     runs-on: ubuntu-latest
     steps:
       - name: Copy repository
@@ -29,8 +34,8 @@ jobs:
         run: yarn test:e2e
         working-directory: ts/server
 
-  Publish:
-    needs: Build
+  publish-fpml-server-ts-to-dockerhub:
+    needs: build-and-test-fpml-server-ts
     if: github.ref == 'refs/heads/main'
     runs-on: ubuntu-latest
     steps:
@@ -48,3 +53,6 @@ jobs:
           docker buildx build --platform linux/arm64,linux/amd64
           --push --tag ${{ env.BUILD_IMAGE }} .
         working-directory: ts/server
+
+  test-fpml-py:
+    uses: ./.github/workflows/test-python.yml

.github/workflows/publish.yml

@@ -0,0 +1,26 @@
+name: publish
+on:
+  push:
+    tags: 
+      - "v*.*.*"
+jobs:
+  test-fpml-py:
+    uses: ./.github/workflows/test-python.yml
+
+  publish-fpml-py-to-pypi:
+    needs: test-fpml-py
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Python 3.11
+        uses: actions/setup-python@v3
+        with:
+          python-version: "3.11"
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install poetry
+      - name: Build a binary wheel and a source tarball
+        run: poetry --project=./python build
+      - name: Publish package
+        uses: pypa/gh-action-pypi-publish@release/v1

.github/workflows/test-python.yml

@@ -0,0 +1,32 @@
+name: test-python
+on: [workflow_call]
+jobs:
+  test-fpml-py:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          - python-version: 3.9
+          - python-version: "3.10"
+          - python-version: "3.11"
+          - python-version: "3.12"
+          - python-version: "3.13"
+    env:
+      PYTHON: ${{ matrix.python-version }}
+    steps:
+      - uses: actions/checkout@v3
+      - name: Python ${{ matrix.python-version }} sample
+        uses: actions/setup-python@v3
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install poetry
+          poetry --project=./python install
+      - name: Run lint
+        run: poetry --project=./python run ruff check ./python
+      - name: Run typecheck
+        run: poetry --project=./python run mypy ./python
+      - name: Run tests
+        run: poetry --project=./python run pytest --cov

.gitignore

@@ -5,3 +5,5 @@ coverage
 htmlcov
 .vscode
 .history
+.coverage
+python/dist

README.md

@@ -547,16 +547,18 @@ that will be transformed into:
 
 ## Examples
 
-See real-life examples of mappers for [FHIR](https://github.com/beda-software/FHIRPathMappingLanguage/blob/main/ts/server/src/utils/__data__/complex-example.fhir.yaml) and [Aidbox](https://github.com/beda-software/FHIRPathMappingLanguage/blob/main/ts/server/src/utils/__data__/complex-example.aidbox.yaml)
+See real-life examples of mappers for [FHIR](https://github.com/beda-software/FHIRPathMappingLanguage/blob/main/tests/__data__/complex-example.fhir.yaml) and [Aidbox](https://github.com/beda-software/FHIRPathMappingLanguage/blob/main/tests/__data__/complex-example.aidbox.yaml)
 
 and other usage in [unit tests](https://github.com/beda-software/FHIRPathMappingLanguage/tree/main/ts/server/src/utils).
 
 ## Reference implementation
 
-TypeScript implementation that supports all the specification is already available [in this repository](https://github.com/beda-software/FHIRPathMappingLanguage/tree/main/server).
+### TypeScript
+
+TypeScript implementation that supports all the specification is already available [in this repository](https://github.com/beda-software/FHIRPathMappingLanguage/tree/main/ts/server).
 Also, it is packed into a [docker image](https://hub.docker.com/r/bedasoftware/fhirpath-extract) to use as a microservice.
 
-### Usage
+#### Usage
 
 POST /r4/parse-template
 
@@ -577,7 +579,7 @@ POST /r4/parse-template
 }
 ```
 
-### Strict mode
+#### Strict mode
 
 FHIRPath provides a way of accessing the `resource` variables without the percent sign. It potentially leads to the issues made by typos in the variable names.
 
@@ -603,4 +605,46 @@ POST /r4/parse-template?strict=true
         "status": "completed"
     }
 }
-```
+```
+
+### Python
+
+Python implementation that supports all the specification is already available [in this repository](https://github.com/beda-software/FHIRPathMappingLanguage/tree/main/python).
+Also, it's available as a PyPI package under the name `fpml` and can be installed using
+```
+pip install fpml
+```
+
+#### Usage
+
+```python
+from fpml import resolve_template
+
+
+resource = {
+    "resourceType": "QuestionnaireResponse",
+    "status": "completed",
+    "item": [
+        {
+            "linkId": "name",
+            "answer": [
+                {
+                    "valueString": "Name"
+                }
+            ]
+        }
+    ]
+}
+
+template = {
+    "resourceType": "Patient",
+    "name": "{{ item.where(linkId='name').answer.valueString }}"
+}
+
+context = {}
+
+result = resolve_template(resource, template, context)
+
+print(result)
+# {'resourceType': 'Patient', 'name': 'Name'}
+```

python/pydian_repeatable.py → examples/python/pydian_repeatable.py

@@ -1,4 +1,4 @@
-from pydian import DROP, Mapper, get
+from pydian import get
 
 
 def map(qr):

examples/python/pyproject.toml

@@ -0,0 +1,28 @@
+[tool.black]
+line-length = 100
+target-version = ['py311']
+exclude = '''
+(
+  /(
+    | \.git
+    | \.pytest_cache
+    | htmlcov
+    | locales
+    | resources
+    | requirements
+    | embed
+  )/
+)
+'''
+
+[tool.isort]
+multi_line_output = 3
+include_trailing_comma = true
+use_parentheses = true
+line_length = 100
+default_section = "THIRDPARTY"
+known_first_party = []
+
+[tool.autohooks]
+mode = "pythonpath"
+pre-commit = ["autohooks.plugins.black", "autohooks.plugins.isort"]

python/.gitignore

@@ -0,0 +1,3 @@
+dev.code-workspace
+.mypy_cache
+__pycache__

python/README.md

@@ -0,0 +1,57 @@
+# FHIRPathMappingLanguage - fpml python package
+
+## Installation
+
+```bash
+pip install fpml
+```
+
+## Usage
+
+```python
+from fpml import resolve_template
+
+
+resource = {
+    "resourceType": "QuestionnaireResponse",
+    "status": "completed",
+    "item": [
+        {
+            "linkId": "name",
+            "answer": [
+                {
+                    "valueString": "Name"
+                }
+            ]
+        }
+    ]
+}
+
+template = {
+    "resourceType": "Patient",
+    "name": "{{ item.where(linkId='name').answer.valueString }}"
+}
+
+context = {}
+
+result = resolve_template(resource, template, context)
+
+print(result)
+# {'resourceType': 'Patient', 'name': 'Name'}
+```
+
+
+## Development
+
+In `./python` directory:
+
+Run in the shell
+```
+autohooks activate
+```
+
+And edit `../.git/hooks/pre-commit` by replacing the first line with
+```
+#!/usr/bin/env -S poetry --project=./python run python
+```
+

python/fpml/__init__.py

@@ -0,0 +1,12 @@
+import importlib.metadata
+
+from .core.exceptions import FPMLValidationError
+from .core.extract import resolve_template
+
+__title__ = "fpml"
+__version__ = importlib.metadata.version("fpml")
+__author__ = "beda.software"
+__license__ = "MIT"
+__copyright__ = "Copyright 2025 beda.software"
+
+__all__ = ["FPMLValidationError", "resolve_template"]

python/fpml/core/constants.py

@@ -0,0 +1,5 @@
+# special root node key for the simplification
+root_node_key = "__rootNode__"
+
+# undefined is a special object used to remove keys from the object (similar to JS)
+undefined = object()

python/fpml/core/exceptions.py

@@ -0,0 +1,11 @@
+from .constants import root_node_key
+from .types import Path
+
+
+class FPMLValidationError(Exception):
+    def __init__(self, message: str, path: Path) -> None:
+        path_str = ".".join(str(x) for x in path if x != root_node_key)
+        super().__init__(f"{message}. Path '{path_str}'")
+
+        self.error_message = message
+        self.error_path = path_str