mirror of
https://github.com/google/flatbuffers.git
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c526cb640b
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")
```
109 lines
3.1 KiB
Python
109 lines
3.1 KiB
Python
# automatically generated by the FlatBuffers compiler, do not modify
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# namespace: Example
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import flatbuffers
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from flatbuffers.compat import import_numpy
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np = import_numpy()
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class Vec3(object):
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__slots__ = ['_tab']
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@classmethod
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def SizeOf(cls):
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return 32
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# Vec3
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def Init(self, buf, pos):
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self._tab = flatbuffers.table.Table(buf, pos)
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# Vec3
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def X(self): return self._tab.Get(flatbuffers.number_types.Float32Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(0))
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# Vec3
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def Y(self): return self._tab.Get(flatbuffers.number_types.Float32Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(4))
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# Vec3
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def Z(self): return self._tab.Get(flatbuffers.number_types.Float32Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(8))
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# Vec3
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def Test1(self): return self._tab.Get(flatbuffers.number_types.Float64Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(16))
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# Vec3
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def Test2(self): return self._tab.Get(flatbuffers.number_types.Uint8Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(24))
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# Vec3
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def Test3(self, obj):
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obj.Init(self._tab.Bytes, self._tab.Pos + 26)
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return obj
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def CreateVec3(builder, x, y, z, test1, test2, test3_a, test3_b):
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builder.Prep(8, 32)
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builder.Pad(2)
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builder.Prep(2, 4)
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builder.Pad(1)
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builder.PrependInt8(test3_b)
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builder.PrependInt16(test3_a)
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builder.Pad(1)
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builder.PrependUint8(test2)
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builder.PrependFloat64(test1)
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builder.Pad(4)
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builder.PrependFloat32(z)
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builder.PrependFloat32(y)
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builder.PrependFloat32(x)
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return builder.Offset()
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import MyGame.Example.Test
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try:
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from typing import Optional
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except:
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pass
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class Vec3T(object):
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# Vec3T
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def __init__(
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self,
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x = 0.0,
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y = 0.0,
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z = 0.0,
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test1 = 0.0,
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test2 = 0,
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test3 = None,
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):
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self.x = x # type: float
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self.y = y # type: float
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self.z = z # type: float
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self.test1 = test1 # type: float
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self.test2 = test2 # type: int
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self.test3 = test3 # type: Optional[MyGame.Example.Test.TestT]
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@classmethod
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def InitFromBuf(cls, buf, pos):
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vec3 = Vec3()
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vec3.Init(buf, pos)
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return cls.InitFromObj(vec3)
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@classmethod
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def InitFromPackedBuf(cls, buf, pos=0):
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n = flatbuffers.encode.Get(flatbuffers.packer.uoffset, buf, pos)
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return cls.InitFromBuf(buf, pos+n)
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@classmethod
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def InitFromObj(cls, vec3):
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x = Vec3T()
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x._UnPack(vec3)
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return x
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# Vec3T
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def _UnPack(self, vec3):
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if vec3 is None:
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return
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self.x = vec3.X()
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self.y = vec3.Y()
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self.z = vec3.Z()
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self.test1 = vec3.Test1()
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self.test2 = vec3.Test2()
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if vec3.Test3(MyGame.Example.Test.Test()) is not None:
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self.test3 = MyGame.Example.Test.TestT.InitFromObj(vec3.Test3(MyGame.Example.Test.Test()))
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# Vec3T
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def Pack(self, builder):
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return CreateVec3(builder, self.x, self.y, self.z, self.test1, self.test2, self.test3.a, self.test3.b)
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