Protobuf Language Guide

Scalar Value Types

.proto Type	C++ Type	Java/Kotlin Type	Python Type	Go Type	Ruby Type	C# Type	PHP Type	Dart Type
double	double	double	float	float64	Float	double	float	double
float	float	float	float	float32	Float	float	float	double
int32	int32	int	int	int32	Fixnum or Bignum (as required)	int	integer	int
int64	int64	long	int/long	int64	Bignum	long	integer/string	Int64
uint32	uint32	int	int/long	uint32	Fixnum or Bignum (as required)	uint	integer	int
uint64	uint64	long	int/long	uint64	Bignum	ulong	integer/string	Int64
sint32	int32	int	int	int32	Fixnum or Bignum (as required)	int	integer	int
sint64	int64	long	int/long	int64	Bignum	long	integer/string	Int64
fixed32	uint32	int	int/long	uint32	Fixnum or Bignum (as required)	uint	integer	int
fixed64	uint64	long	int/long	uint64	Bignum	ulong	integer/string	Int64
sfixed32	int64	long	int/long	int64	Bignum	long	integer/string	Int64
bool	bool	boolean	bool	bool	TrueClass/FalseClass	bool	boolean	bool
string	string	String	str/unicode	string	String (UTF-8)	string	string	String
bytes	string	ByteString	str	[]byte	String (ASCII-8BIT)	ByteString	string	List

For strings, the default value is the empty string.
For bytes, the default value is empty bytes.
For bools, the default value is false.
For numeric types, the default value is zero.
For enums, the default value is the first defined enum value, which must be 0.
For message fields, the field is not set. Its exact value is language-dependent. See the generated code guide for details.