Data Types

Data Types Supported by Python Parser

Similar to Python, Python Parser supports various data types, including integers, floating-point numbers, strings, booleans, null values, variables, and constants. The difference lies in that Python Parser's data types are compatible with DolphinDB's. For instance, None in Python Parser corresponds to VOID in DolphinDB; the integer precision in Python Parser is consistent with that in DolphinDB, rather than unlimited as in Python.

The following table compares the data types in DolphinDB, Python Parser, and Python (Empty cells in the "Python" column indicate data types not supported by Python):


Data Type	DolphinDB	Python Parser	Python
VOID	NULL	None	None
BOOL	1b, 0b, true, false	1b, 0b, True, False, bool(1)	True, False
CHAR	'a', 97c	97c, char('a')
SHORT	122h	122h
INT	21	21	21
LONG	22l	22l
DATE	2013.06.13	2013.06.13	2013-06-13
MONTH	2012.06M	2012.06M	2012-06
TIME	13:30:10.008	13:30:10.008	13:30:10.008
MINUTE	13:30m	13:30m	13:30
SECOND	13:30:10	13:30:10	13:30:10
DATETIME	2012.06.13 13:30:10 or 2012.06.13T13:30:10	2012.06.13 13:30:10 or 2012.06.13T13:30:10	2012-06-13 13:30:10
TIMESTAMP	2012.06.13 13:30:10.008 or 2012.06.13T13:30:10.008	2012.06.13 13:30:10.008 or 2012.06.13T13:30:10.008	2012-06-13 13:30:10.008000
NANOTIME	13:30:10.008007006	13:30:10.008007006	13:30:10.008007006
NANOTIMESTAMP	2012.06.13 13:30:10.008007006 or 2012.06.13T13:30:10.008007006	2012.06.13 13:30:10.008007006 or 2012.06.13T13:30:10.008007006	2012.06.13 13:30:10.008007006
FLOAT	2.1f (single precision)	2.1f (single precision)	2.1 (double precision)
DOUBLE	2.1, 2.1F (double precision)	2.1, 2.1F (double precision)
SYMBOL	symbol([`A,`B,`C])	symbol([`A,`B,`C].toddb())
STRING	"Hello" or 'Hello' or `Hello	"Hello" or 'Hello' or `Hello or """Hello""" or '''Hello'''	"Hello" or 'Hello' or """Hello""" or '''Hello'''
UUID	uuid("9d457e79-1bed-d6c2-3612-b0d31c1881f6")	uuid("9d457e79-1bed-d6c2-3612-b0d31c1881f6")	9d457e79-1bed-d6c2-3612-b0d31c1881f6
FUNCTIONDEF	def f1(a,b) {return a+b;}	def f1(a,b): return a+b
HANDLE	file handle, socket handle, and db handle	file handle, socket handle, and db handle
CODE	<1+2>	<1+2>
DATASOURCE	data source	data source
RESOURCE	model (kmeans)	model (kmeans)
ANY	(1,2,3)	(1,2,3)	(1,2,3)
COMPRESSED	compress(seq(1,10), "delta")	compress(seq(1,10), "delta")
ANY DICTIONARY	{"a":1,"b":2}	{"a":1,"b":2}	{"a":1,"b":2}
DATEHOUR	datehour(2012.06.13 13:30:10) or datehour(2012.06.13T13:30:10)	Generated by the `datehour` function in DolphinDB: datehour(2012.06.13 13:30:10) or datehour(2012.06.13T13:30:10)	2012-06-13 13:30:10
IPADDR	ipaddr("192.168.1.13")	ipaddr("192.168.1.13")	ipaddress.IPv4Address("192.168.1.13")
INT128	int128("e1671797c52e15f763380b45e841ec32")	int128("e1671797c52e15f763380b45e841ec32")
BLOB	blob(str)	blob(str)
COMPLEX	complex(2, 5)	complex(2, 5)	complex(2, 5)
POINT	point(117.60972, 24.118418)	point(117.60972, 24.118418)
DURATION	1s, 3M, 5y, 200ms	1s, 3M, 5y, 200ms
DECIMAL32(S)	3.1415926$DECIMAL32(3), decimal32(3.1415926, 3)	decimal32(3.1415926, 3)	decimal.Decimal(3.1415926) DECIMAL in Python does not specify fixed-bit representations like DECIMAL32/64/128. Its maximum number of bits is determined by the Python version and the underlying hardware.
DECIMAL64(S)	3.1415926$DECIMAL64(3), 3.141P, decimal64(3.1415926, 3)	decimal64(3.1415926, 3)
DECIMAL128(S)	3.1415926$DECIMAL128(3), decimal128(3.1415926, 3)	decimal128(3.1415926, 3)

Data Type Query

The type function can be used to query the data type of an object, as shown below:

type(None)

Output: dolphindb.SCALAR.VOID

Reserved Word

Constant Reserved Word

Python Parser supports specific reserved words in Python, such as "True", "False", "None", etc., and is compatible with constant reserved words in DolphinDB, as shown in the following table:


Python	DolphinDB
True	ddb.true
False	ddb.false
None	ddb.VOID

To call DolphinDB's built-in functions, the dolphindb module can be used to import reserved words exclusive to DolphinDB, as shown in the following script:

import dolphindb as ddb
ddb.NULL
ddb.VOID
ddb.pi
ddb.e
ddb.HINT_KEEPORDER
ddb.RANGE
...

Use the is operator to determine whether two variables reference the same object.

None is ddb.VOID

Output: true

None is ddb.NULL

Output: false

Programming Reserved Word

Python Parser supports most programming reserved words in Python and DolphinDB, except global, nonlocal, del, yield, match, async, await, and with.

def zero(s):
    a = int(s)
    assert a > 0,"a is out of range"   
    return a

zero("-2")

Output: Testing case adhocTesting_"a is out of range" failed

n = 0
while n < 10:
    n = n + 1
    if n % 2 == 0:      
        continue        
    print(n)

Output:

The raise statement in Python Parser only supports raising an exception with a message, as shown below:

def test_exception():
    try:
            raise "asdf"
    except Exception as ex:
            assert ex[0]=="USER"
    
    print("test_exception test pass")

test_exception()