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[Python] Optimize Builder startup: lazy sharedStrings and fast vtable init #8807

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Merged
jtdavis777 merged 2 commits into from
Nov 30, 2025
Merged

[Python] Optimize Builder startup: lazy sharedStrings and fast vtable init #8807

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b8eb562
Optimize Builder startup: lazy sharedStrings and fast vtable init
satur9nine Nov 27, 2025
6511e7c
Merge branch 'master' into python-perf-startup
jtdavis777 Nov 30, 2025
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10 changes: 6 additions & 4 deletions python/flatbuffers/builder.py
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Original file line number Diff line number Diff line change
Expand Up @@ -159,7 +159,7 @@ def __init__(self, initialSize=1024):
self.vtables = {}
self.nested = False
self.forceDefaults = False
self.sharedStrings = {}
self.sharedStrings = None
## @endcond
self.finished = False

Expand All @@ -172,7 +172,7 @@ def Clear(self):
self.vtables = {}
self.nested = False
self.forceDefaults = False
self.sharedStrings = {}
self.sharedStrings = None
self.vectorNumElems = None
## @endcond
self.finished = False
Expand Down Expand Up @@ -201,7 +201,7 @@ def StartObject(self, numfields):
self.assertNotNested()

# use 32-bit offsets so that arithmetic doesn't overflow.
self.current_vtable = [0 for _ in range_func(numfields)]
self.current_vtable = [0] * numfields
self.objectEnd = self.Offset()
self.nested = True

Expand Down Expand Up @@ -457,7 +457,9 @@ def CreateSharedString(self, s, encoding="utf-8", errors="strict"):
before calling CreateString.
"""

if s in self.sharedStrings:
if not self.sharedStrings:
self.sharedStrings = {}
elif s in self.sharedStrings:
return self.sharedStrings[s]

off = self.CreateString(s, encoding, errors)
Expand Down
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