forked from BigfootDev/flatbuffers
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")
```
166 lines
5.1 KiB
Python
166 lines
5.1 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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from typing import Any
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np = import_numpy()
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class NestedStruct(object):
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__slots__ = ['_tab']
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@classmethod
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def SizeOf(cls) -> int:
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return 32
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# NestedStruct
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def Init(self, buf: bytes, pos: int):
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self._tab = flatbuffers.table.Table(buf, pos)
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# NestedStruct
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def A(self, j = None):
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if j is None:
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return [self._tab.Get(flatbuffers.number_types.Int32Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(0 + i * 4)) for i in range(self.ALength())]
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elif j >= 0 and j < self.ALength():
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return self._tab.Get(flatbuffers.number_types.Int32Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(0 + j * 4))
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else:
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return None
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# NestedStruct
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def AAsNumpy(self):
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return self._tab.GetArrayAsNumpy(flatbuffers.number_types.Int32Flags, self._tab.Pos + 0, self.ALength())
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# NestedStruct
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def ALength(self) -> int:
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return 2
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# NestedStruct
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def AIsNone(self) -> bool:
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return False
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# NestedStruct
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def B(self): return self._tab.Get(flatbuffers.number_types.Int8Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(8))
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# NestedStruct
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def C(self, j = None):
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if j is None:
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return [self._tab.Get(flatbuffers.number_types.Int8Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(9 + i * 1)) for i in range(self.CLength())]
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elif j >= 0 and j < self.CLength():
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return self._tab.Get(flatbuffers.number_types.Int8Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(9 + j * 1))
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else:
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return None
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# NestedStruct
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def CAsNumpy(self):
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return self._tab.GetArrayAsNumpy(flatbuffers.number_types.Int8Flags, self._tab.Pos + 9, self.CLength())
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# NestedStruct
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def CLength(self) -> int:
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return 2
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# NestedStruct
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def CIsNone(self) -> bool:
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return False
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# NestedStruct
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def D(self, j = None):
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if j is None:
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return [self._tab.Get(flatbuffers.number_types.Int64Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(16 + i * 8)) for i in range(self.DLength())]
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elif j >= 0 and j < self.DLength():
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return self._tab.Get(flatbuffers.number_types.Int64Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(16 + j * 8))
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else:
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return None
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# NestedStruct
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def DAsNumpy(self):
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return self._tab.GetArrayAsNumpy(flatbuffers.number_types.Int64Flags, self._tab.Pos + 16, self.DLength())
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# NestedStruct
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def DLength(self) -> int:
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return 2
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# NestedStruct
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def DIsNone(self) -> bool:
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return False
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def CreateNestedStruct(builder, a, b, c, d):
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builder.Prep(8, 32)
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for _idx0 in range(2 , 0, -1):
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builder.PrependInt64(d[_idx0-1])
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builder.Pad(5)
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for _idx0 in range(2 , 0, -1):
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builder.PrependInt8(c[_idx0-1])
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builder.PrependInt8(b)
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for _idx0 in range(2 , 0, -1):
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builder.PrependInt32(a[_idx0-1])
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return builder.Offset()
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try:
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from typing import List
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except:
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pass
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class NestedStructT(object):
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# NestedStructT
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def __init__(
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self,
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a = None,
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b = 0,
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c = None,
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d = None,
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):
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self.a = a # type: Optional[List[int]]
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self.b = b # type: int
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self.c = c # type: Optional[List[int]]
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self.d = d # type: Optional[List[int]]
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@classmethod
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def InitFromBuf(cls, buf, pos):
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nestedStruct = NestedStruct()
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nestedStruct.Init(buf, pos)
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return cls.InitFromObj(nestedStruct)
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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, nestedStruct):
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x = NestedStructT()
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x._UnPack(nestedStruct)
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return x
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# NestedStructT
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def _UnPack(self, nestedStruct):
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if nestedStruct is None:
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return
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if not nestedStruct.AIsNone():
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if np is None:
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self.a = []
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for i in range(nestedStruct.ALength()):
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self.a.append(nestedStruct.A(i))
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else:
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self.a = nestedStruct.AAsNumpy()
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self.b = nestedStruct.B()
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if not nestedStruct.CIsNone():
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if np is None:
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self.c = []
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for i in range(nestedStruct.CLength()):
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self.c.append(nestedStruct.C(i))
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else:
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self.c = nestedStruct.CAsNumpy()
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if not nestedStruct.DIsNone():
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if np is None:
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self.d = []
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for i in range(nestedStruct.DLength()):
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self.d.append(nestedStruct.D(i))
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else:
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self.d = nestedStruct.DAsNumpy()
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# NestedStructT
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def Pack(self, builder):
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return CreateNestedStruct(builder, self.a, self.b, self.c, self.d)
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