This commit significantly improves the developer experience for the Python Object-Based API by overhauling the generated `__init__` method for `T`-suffixed classes.
Previously, `T` objects had to be instantiated with an empty constructor, and their fields had to be populated manually one by one. This was verbose and not idiomatic Python.
This change modifies the Python code generator (`GenInitialize`) to produce `__init__` methods that are:
1. **Keyword-Argument-Friendly**: The constructor now accepts all table/struct fields as keyword arguments, allowing for concise, single-line object creation.
2. **Fully Typed**: The signature of the `__init__` method is now annotated with Python type hints. This provides immediate benefits for static analysis tools (like Mypy) and IDEs, enabling better autocompletion and type checking.
3. **Correctly Optional**: The generator now correctly wraps types in `Optional[...]` if their default value is `None`. This applies to strings, vectors, and other nullable fields, ensuring strict type safety.
The new approach remains **fully backward-compatible**, as all arguments have default values. Existing code that uses the empty constructor will continue to work without modification.
#### Example of a Generated `__init__`
**Before:**
```python
class KeyValueT(object):
def __init__(self):
self.key = None # type: str
self.value = None # type: str
```
**After:**
```python
class KeyValueT(object):
def __init__(self, key: Optional[str] = None, value: Optional[str] = None):
self.key = key
self.value = value
```
#### Example of User Code
**Before:**
```python
# Old, verbose way
kv = KeyValueT()
kv.key = "instrument"
kv.value = "EUR/USD"
```
**After:**
```python
# New, Pythonic way
kv = KeyValueT(key="instrument", value="EUR/USD")
```
This prevents the include of the type defined in the pyi,
otherwise this leads to error message like this:
error: Name XYZ already defined (possibly by an import) [no-redef]
* [Python] Generate `.pyi` stub files when `--python-typing` is on.
To support this change, the following modifications were made:
- added a new option to disable `numpy` helpers generation;
- added a new flag to control the target Python version:
`--python-version` can be one of the following:
- `0.x.x` – compatible with any Python version;
- `2.x.x` – compatible with Python 2;
- `3.x.x` – compatible with Python 3.
- added codegen utilities for Python;
- added a note that the generated .py file is empty.
* [Python] Update Bazel build rules.
* [Python] Update Bazel build rules.
* [Python] Run buildifier on BUILD.bazel files.
---------
Co-authored-by: Derek Bailey <derekbailey@google.com>
