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Fix deserialization of numbers with trailing zeros from DynamoDB by normalizing first #4694

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Fix deserialization of numbers with trailing zeros from DynamoDB by normalizing first #4694

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Fix deserialization of numbers with trailing zeros from DynamoDB by n…
rowanseymour Jan 7, 2026
0f924db
Add more test cases
rowanseymour Jan 7, 2026
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2 changes: 1 addition & 1 deletion boto3/dynamodb/types.py
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Original file line number Diff line number Diff line change
Expand Up @@ -286,7 +286,7 @@ def _deserialize_bool(self, value):
return value

def _deserialize_n(self, value):
return DYNAMODB_CONTEXT.create_decimal(value)
return DYNAMODB_CONTEXT.create_decimal(Decimal(value).normalize())

def _deserialize_s(self, value):
return value
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4 changes: 4 additions & 0 deletions tests/unit/dynamodb/test_types.py
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Expand Up @@ -167,6 +167,10 @@ def test_deserialize_integer(self):

def test_deserialize_decimal(self):
assert self.deserializer.deserialize({'N': '1.25'}) == Decimal('1.25')
assert self.deserializer.deserialize({'N': '1.2500'}) == Decimal('1.25')
assert self.deserializer.deserialize({'N': '1234567891234560000000000000000000000000'}) == Decimal('1.23456789123456E+39')
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Copilot AI Jan 7, 2026

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The test uses a different number than the one mentioned in the linked issue (#4693). The issue reports 1234567895171680000000000000000000000000 but this test uses 1234567891234560000000000000000000000000. Consider adding a test case with the exact number from the issue to ensure it's properly fixed.

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Copilot AI Jan 7, 2026

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Consider adding test cases for additional edge cases with trailing zeros to ensure comprehensive coverage:

  • Numbers with trailing zeros after the decimal point (e.g., '1.2500')
  • Negative numbers with trailing zeros (e.g., '-1234567891234560000000000000000000000000')
  • Numbers already in scientific notation (e.g., '1.23E+39')
  • Very small numbers with trailing zeros (e.g., '0.00001000')

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assert self.deserializer.deserialize({'N': '-1234567891234560000000000000000000000000'}) == Decimal('-1.23456789123456E+39')
assert self.deserializer.deserialize({'N': '1.23E+39'}) == Decimal('1.23E+39')

def test_deserialize_string(self):
assert self.deserializer.deserialize({'S': 'foo'}) == 'foo'
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