Reference Manual¶

(This section is generated from the PyQ source code. You can access most of this material using pydoc or the built-in help method.)

`K`	proxies for kdb+ objects
`q`	a portal to kdb+

class K¶

class pyq.K¶

proxies for kdb+ objects

>>> q('2005.01.01 2005.12.04')
k('2005.01.01 2005.12.04')

Iteration over simple lists produces python objects

>>> list(q("`a`b`c`d"))
['a', 'b', 'c', 'd']

Iteration over q tables produces q dictionaries

>>> list(q("([]a:`x`y`z;b:1 2 3)"))
[k('`a`b!(`x;1)'), k('`a`b!(`y;2)'), k('`a`b!(`z;3)')]

Iteration over a q dictionary iterates over its key

>>> list(q('`a`b!1 2'))
['a', 'b']

as a consequence, iteration over a keyed table is the same as iteration over its key table

>>> list(q("([a:`x`y`z]b:1 2 3)"))
[k('(,`a)!,`x'), k('(,`a)!,`y'), k('(,`a)!,`z')]

Callbacks into python

>>> def f(x, y):
...     return x + y
>>> q('{[f]f(1;2)}', f)
k('3')

Buffer protocol

The following session illustrates how buffer protocol implemented by K objects can be used to write data from Python streams directly yo kdb+.

Create a list of chars in kdb+

>>> x = kp('xxxxxx')

Open a pair of file descriptors

>>> r, w = os.pipe()

Write 6 bytes to the write end

>>> os.write(w, b'abcdef')
6

Read from the read-end into x

>>> f = os.fdopen(r, mode='rb')
>>> f.readinto(x)
6

Now x contains the bytes that were sent through the pipe

>>> x
k('"abcdef"')

Close the descriptors and the stream

>>> os.close(w); f.close()

Low level interface

The K type provides a set of low level functions that are similar to the C API provided by the k.h header. The C API functions that return K objects in C are implemented as class methods that return instances of K type.

Atoms

>>> K._kb(True), K._kg(5), K._kh(42), K._ki(-3), K._kj(2**40)
(k('1b'), k('0x05'), k('42h'), k('-3i'), k('1099511627776'))

>>> K._ke(3.5), K._kf(1.0), K._kc(b'x'), K._ks('xyz')
(k('3.5e'), k('1f'), k('"x"'), k('`xyz'))

>>> K._kd(0), K._kz(0.0), K._kt(0)
(k('2000.01.01'), k('2000.01.01T00:00:00.000'), k('00:00:00.000'))

Tables and dictionaries

>>> x = K._xD(k('`a`b`c'), k('1 2 3')); x, K._xT(x)
(k('`a`b`c!1 2 3'), k('+`a`b`c!1 2 3'))

Keyed table

>>> t = K._xD(K._xT(K._xD(k(",`a"), k(",1 2 3"))),
...           K._xT(K._xD(k(",`b"), k(",10 20 30"))))
>>> K._ktd(t)
k('+`a`b!(1 2 3;10 20 30)')

K objects can be used in Python arithmetic expressions

>>> x, y, z = map(K, (1, 2, 3))
>>> print(x + y, x * y,
...       z/y, x|y, x&y, abs(-z))  
3 2 1.5 2 1 3

Mixing K objects with python numbers is allowed

>>> 1/q('1 2 4')
k('1 0.5 0.25')
>>> q.til(5)**2
k('0 1 4 9 16f')

__call__¶: Call self as a function.

__contains__(item)¶

membership test

>>> 1 in q('1 2 3')
True

>>> 'abc' not in q('(1;2.0;`abc)')
False

__eq__(other)¶

>>> K(1) == K(1)
True
>>> K(1) == None
False

__float__()¶

converts K scalars to python float

>>> [float(q(x)) for x in '1b 2h 3 4e `5 6.0 2000.01.08'.split()]
[1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0]

__get__¶: Return an attribute of instance, which is of type owner.

__getattr__(a)¶

table columns can be accessed via dot notation

>>> q("([]a:1 2 3; b:10 20 30)").a
k('1 2 3')

__getitem__(x)¶

>>> k("10 20 30 40 50")[k("1 3")]
k('20 40')
>>> k("`a`b`c!1 2 3")['b']
2

__int__()¶

converts K scalars to python int

>>> [int(q(x)) for x in '1b 2h 3 4e `5 6.0 2000.01.08'.split()]
[1, 2, 3, 4, 5, 6, 7]

exec(columns=(), by=(), where=(), **kwds)¶

exec from self

>>> t = q('([]a:1 2 3; b:10 20 30)')
>>> t.exec_('a', where='b > 10').show()
2 3

keys()¶

returns q(‘key’, self)

Among other uses, enables interoperability between q and python dicts.

>>> from collections import OrderedDict
>>> OrderedDict(q('`a`b!1 2'))
OrderedDict([('a', 1), ('b', 2)])
>>> d = {}; d.update(q('`a`b!1 2'))
>>> list(sorted(d.items()))
[('a', 1), ('b', 2)]

select(columns=(), by=(), where=(), **kwds)¶

select from self

>>> t = q('([]a:1 2 3; b:10 20 30)')
>>> t.select('a', where='b > 20').show()
a
-
3

show(start=0, geometry=None, output=None)¶

pretty-print data to the console

(similar to q.show, but uses python stdout by default)

>>> x = q('([k:`x`y`z]a:1 2 3;b:10 20 30)')
>>> x.show()  
k| a b
-| ----
x| 1 10
y| 2 20
z| 3 30

the first optional argument, ‘start’ specifies the first row to be printed (negative means from the end)

>>> x.show(2)  
k| a b
-| ----
z| 3 30

>>> x.show(-2)  
k| a b
-| ----
y| 2 20
z| 3 30

the geometry is the height and width of the console

>>> x.show(geometry=[4, 6])
k| a..
-| -..
x| 1..
..

update(columns=(), by=(), where=(), **kwds)¶

update from self

>>> t = q('([]a:1 2 3; b:10 20 30)')
>>> t.update('a*2',
...          where='b > 20').show()  
a b
----
1 10
2 20
6 30

K.abs()¶

absolute value

For details, see q.abs and abs on code.kx.com.

K.acos()¶

arc cosine

For details, see q.acos and acos on code.kx.com.

K.aj()¶

as-of join

For details, see q.aj and aj on code.kx.com.

K.aj0()¶

as-of join

For details, see q.aj0 and aj on code.kx.com.

K.all()¶

all nonzero

For details, see q.all and all on code.kx.com.

K.and_()¶

and

For details, see q.and_ and and on code.kx.com.

K.any()¶

any item is non-zero

For details, see q.any and any on code.kx.com.

K.asc()¶

ascending sort

For details, see q.asc and asc on code.kx.com.

K.asin()¶

arc sine

For details, see q.asin and asin on code.kx.com.

K.asof()¶

as-of operator

For details, see q.asof and asof on code.kx.com.

K.atan()¶

arc tangent

For details, see q.atan and atan on code.kx.com.

K.attr()¶

attributes

For details, see q.attr and attr on code.kx.com.

K.avg()¶

arithmetic mean

For details, see q.avg and avg on code.kx.com.

K.avgs()¶

running averages

For details, see q.avgs and avgs on code.kx.com.

K.bin()¶

binary search

For details, see q.bin and bin on code.kx.com.

K.binr()¶

binary search

For details, see q.binr and bin on code.kx.com.

K.ceiling()¶

lowest integer above

For details, see q.ceiling and ceiling on code.kx.com.

K.cols()¶

column names of a table

For details, see q.cols and cols on code.kx.com.

K.cor()¶

correlation

For details, see q.cor and cor on code.kx.com.

K.cos()¶

cosine

For details, see q.cos and cos on code.kx.com.

K.count()¶

number of items

For details, see q.count and count on code.kx.com.

K.cov()¶

statistical covariance

For details, see q.cov and cov on code.kx.com.

K.cross()¶

cross product

For details, see q.cross and cross on code.kx.com.

K.csv()¶

comma delimiter

For details, see q.csv and csv on code.kx.com.

K.cut()¶

cut

For details, see q.cut and cut on code.kx.com.

K.deltas()¶

differences between consecutive pairs

For details, see q.deltas and deltas on code.kx.com.

K.desc()¶

descending sort

For details, see q.desc and desc on code.kx.com.

K.dev()¶

standard deviation

For details, see q.dev and dev on code.kx.com.

K.differ()¶

flag differences in consecutive pairs

For details, see q.differ and differ on code.kx.com.

K.distinct()¶

unique items

For details, see q.distinct and distinct on code.kx.com.

K.div()¶

integer division

For details, see q.div and div on code.kx.com.

K.dsave()¶

save global tables to disk

For details, see q.dsave and dsave on code.kx.com.

K.ej()¶

equi-join

For details, see q.ej and ej on code.kx.com.

K.ema()¶

exponentially-weighted moving average

For details, see q.ema and ema on code.kx.com.

K.ema()

exponentially-weighted moving average

For details, see q.ema and ema on code.kx.com.

K.enlist()¶

arguments as a list

For details, see q.enlist and enlist on code.kx.com.

K.eval()¶

evaluate a parse tree

For details, see q.eval and eval on code.kx.com.

K.except_()¶

left argument without items in right argument

For details, see q.except_ and except on code.kx.com.

K.exp()¶

power of e

For details, see q.exp and exp on code.kx.com.

K.fby()¶

filter-by

For details, see q.fby and fby on code.kx.com.

K.fills()¶

forward-fill nulls

For details, see q.fills and fills on code.kx.com.

K.first()¶

first item

For details, see q.first and first on code.kx.com.

K.fkeys()¶

foreign-key columns mapped to their tables

For details, see q.fkeys and fkeys on code.kx.com.

K.flip()¶

transpose

For details, see q.flip and flip on code.kx.com.

K.floor()¶

greatest integer less than argument

For details, see q.floor and floor on code.kx.com.

K.get()¶

get

For details, see q.get and get on code.kx.com.

K.getenv()¶

value of an environment variable

For details, see q.getenv and getenv on code.kx.com.

K.group()¶

dictionary of distinct items

For details, see q.group and group on code.kx.com.

K.gtime()¶

UTC timestamp

For details, see q.gtime and gtime on code.kx.com.

K.hclose()¶

close a file or process

For details, see q.hclose and hclose on code.kx.com.

K.hcount()¶

size of a file

For details, see q.hcount and hcount on code.kx.com.

K.hdel()¶

delete a file

For details, see q.hdel and hdel on code.kx.com.

K.hopen()¶

open a file

For details, see q.hopen and hopen on code.kx.com.

K.hsym()¶

convert symbol to filename or IP address

For details, see q.hsym and hsym on code.kx.com.

K.iasc()¶

indices of ascending sort

For details, see q.iasc and iasc on code.kx.com.

K.idesc()¶

indices of descending sort

For details, see q.idesc and idesc on code.kx.com.

K.ij()¶

inner join

For details, see q.ij and ij on code.kx.com.

K.ijf()¶

The ijf function.

For details, see q.ijf and ijf on code.kx.com.

K.in_()¶

membership

For details, see q.in_ and in on code.kx.com.

K.insert()¶

append records to a table

For details, see q.insert and insert on code.kx.com.

K.inter()¶

items common to both arguments

For details, see q.inter and inter on code.kx.com.

K.inv()¶

matrix inverse

For details, see q.inv and inv on code.kx.com.

K.key()¶

key

For details, see q.key and key on code.kx.com.

K.keys()

names of a table’s columns

For details, see q.keys and keys on code.kx.com.

K.last()¶

last item

For details, see q.last and last on code.kx.com.

K.like()¶

pattern matching

For details, see q.like and like on code.kx.com.

K.lj()¶

left join

For details, see q.lj and lj on code.kx.com.

K.ljf()¶

left join

For details, see q.ljf and ljf on code.kx.com.

K.load()¶

load binary data

For details, see q.load and load on code.kx.com.

K.log()¶

natural logarithm

For details, see q.log and log on code.kx.com.

K.lower()¶

lower case

For details, see q.lower and lower on code.kx.com.

K.lsq()¶

least squares matrix divide

For details, see q.lsq and lsq on code.kx.com.

K.ltime()¶

local timestamp

For details, see q.ltime and ltime on code.kx.com.

K.ltrim()¶

function remove leading spaces

For details, see q.ltrim and ltrim on code.kx.com.

K.mavg()¶

moving average

For details, see q.mavg and mavg on code.kx.com.

K.max()¶

maximum

For details, see q.max and max on code.kx.com.

K.maxs()¶

maxima of preceding items

For details, see q.maxs and maxs on code.kx.com.

K.mcount()¶

moving count

For details, see q.mcount and mcount on code.kx.com.

K.md5()¶

MD5 hash

For details, see q.md5 and md5 on code.kx.com.

K.mdev()¶

moving deviation

For details, see q.mdev and mdev on code.kx.com.

K.med()¶

median

For details, see q.med and med on code.kx.com.

K.meta()¶

metadata of a table

For details, see q.meta and meta on code.kx.com.

K.min()¶

minimum

For details, see q.min and min on code.kx.com.

K.mins()¶

minimum of preceding items

For details, see q.mins and mins on code.kx.com.

K.mmax()¶

moving maxima

For details, see q.mmax and mmax on code.kx.com.

K.mmin()¶

moving minima

For details, see q.mmin and mmin on code.kx.com.

K.mmu()¶

mmu

For details, see q.mmu and mmu on code.kx.com.

K.mod()¶

remainder

For details, see q.mod and mod on code.kx.com.

K.msum()¶

moving sum

For details, see q.msum and msum on code.kx.com.

K.neg()¶

negate

For details, see q.neg and neg on code.kx.com.

K.next()¶

next items

For details, see q.next and next on code.kx.com.

K.not_()¶

not

For details, see q.not_ and not on code.kx.com.

K.null()¶

null

For details, see q.null and null on code.kx.com.

K.or_()¶

or

For details, see q.or_ and or on code.kx.com.

K.parse()¶

parse a string

For details, see q.parse and parse on code.kx.com.

K.peach()¶

peach

For details, see q.peach and peach on code.kx.com.

K.pj()¶

plus join

For details, see q.pj and pj on code.kx.com.

K.prd()¶

product

For details, see q.prd and prd on code.kx.com.

K.prds()¶

cumulative products

For details, see q.prds and prds on code.kx.com.

K.prev()¶

previous items

For details, see q.prev and prev on code.kx.com.

K.prior()¶

prior

For details, see q.prior and prior on code.kx.com.

K.rand()¶

random number

For details, see q.rand and rand on code.kx.com.

K.rank()¶

grade up

For details, see q.rank and rank on code.kx.com.

K.ratios()¶

ratios of consecutive pairs

For details, see q.ratios and ratios on code.kx.com.

K.raze()¶

join items

For details, see q.raze and raze on code.kx.com.

K.read0()¶

read file as lines

For details, see q.read0 and read0 on code.kx.com.

K.read1()¶

read file as bytes

For details, see q.read1 and read1 on code.kx.com.

K.reciprocal()¶

reciprocal of a number

For details, see q.reciprocal and reciprocal on code.kx.com.

K.reval()¶

variation of eval

For details, see q.reval and reval on code.kx.com.

K.reverse()¶

reverse the order of items

For details, see q.reverse and reverse on code.kx.com.

K.rload()¶

load a splayed table

For details, see q.rload and rload on code.kx.com.

K.rotate()¶

rotate items

For details, see q.rotate and rotate on code.kx.com.

K.rsave()¶

rsave

For details, see q.rsave and rsave on code.kx.com.

K.rtrim()¶

remove trailing spaces

For details, see q.rtrim and rtrim on code.kx.com.

K.save()¶

save global data to file

For details, see q.save and save on code.kx.com.

K.scov()¶

statistical covariance

For details, see q.scov and scov on code.kx.com.

K.scov()

statistical covariance

For details, see q.scov and scov on code.kx.com.

K.sdev()¶

statistical standard deviation

For details, see q.sdev and sdev on code.kx.com.

K.sdev()

statistical standard deviation

For details, see q.sdev and sdev on code.kx.com.

K.set()¶

set

For details, see q.set and set on code.kx.com.

K.setenv()¶

set an environment variable

For details, see q.setenv and setenv on code.kx.com.

K.show()

format to the console

For details, see q.show and show on code.kx.com.

K.signum()¶

sign of its argument/s

For details, see q.signum and signum on code.kx.com.

K.sin()¶

sine

For details, see q.sin and sin on code.kx.com.

K.sqrt()¶

square root

For details, see q.sqrt and sqrt on code.kx.com.

K.ss()¶

string search

For details, see q.ss and ss on code.kx.com.

K.ssr()¶

string search and replace

For details, see q.ssr and ssr on code.kx.com.

K.string()¶

cast to string

For details, see q.string and string on code.kx.com.

K.sublist()¶

sublist of a list

For details, see q.sublist and sublist on code.kx.com.

K.sum()¶

sum of a list

For details, see q.sum and sum on code.kx.com.

K.sums()¶

cumulative sums of a list

For details, see q.sums and sums on code.kx.com.

K.sv()¶

consolidate

For details, see q.sv and sv on code.kx.com.

K.svar()¶

statistical variance

For details, see q.svar and svar on code.kx.com.

K.svar()

statistical variance

For details, see q.svar and svar on code.kx.com.

K.system()¶

system

For details, see q.system and system on code.kx.com.

K.tables()¶

sorted list of tables

For details, see q.tables and tables on code.kx.com.

K.tan()¶

tangent

For details, see q.tan and tan on code.kx.com.

K.til()¶

integers up to x

For details, see q.til and til on code.kx.com.

K.trim()¶

remove leading and trailing spaces

For details, see q.trim and trim on code.kx.com.

K.type()¶

data type

For details, see q.type and type on code.kx.com.

K.uj()¶

union join

For details, see q.uj and uj on code.kx.com.

K.ujf()¶

The ujf function.

For details, see q.ujf and ujf on code.kx.com.

K.ungroup()¶

flattened table

For details, see q.ungroup and ungroup on code.kx.com.

K.union()¶

distinct items of combination of two lists

For details, see q.union and union on code.kx.com.

K.upper()¶

upper-case

For details, see q.upper and upper on code.kx.com.

K.upsert()¶

add table records

For details, see q.upsert and upsert on code.kx.com.

K.value()¶

value

For details, see q.value and value on code.kx.com.

K.var()¶

variance

For details, see q.var and var on code.kx.com.

K.view()¶

definition of a dependency

For details, see q.view and view on code.kx.com.

K.views()¶

list of defined views

For details, see q.views and views on code.kx.com.

K.vs()¶

split

For details, see q.vs and vs on code.kx.com.

K.wavg()¶

weighted average

For details, see q.wavg and wavg on code.kx.com.

K.where()¶

replicated items

For details, see q.where and where on code.kx.com.

K.within()¶

flag items within range

For details, see q.within and within on code.kx.com.

K.wj()¶

window join

For details, see q.wj and wj on code.kx.com.

K.wj1()¶

window join

For details, see q.wj1 and wj1 on code.kx.com.

K.wsum()¶

weighted sum

For details, see q.wsum and wsum on code.kx.com.

K.ww()¶

The ww function.

For details, see q.ww and ww on code.kx.com.

K.xasc()¶

table sorted ascending by columns

For details, see q.xasc and xasc on code.kx.com.

K.xbar()¶

interval bar

For details, see q.xbar and xbar on code.kx.com.

K.xcol()¶

rename table columns

For details, see q.xcol and xcol on code.kx.com.

K.xcols()¶

re-order table columns

For details, see q.xcols and xcols on code.kx.com.

K.xdesc()¶

table sorted descending by columns

For details, see q.xdesc and xdesc on code.kx.com.

K.xexp()¶

raised to a power

For details, see q.xexp and xexp on code.kx.com.

K.xgroup()¶

table grouped by keys

For details, see q.xgroup and xgroup on code.kx.com.

K.xkey()¶

set primary keys of a table

For details, see q.xkey and xkey on code.kx.com.

K.xlog()¶

base-x logarithm

For details, see q.xlog and xlog on code.kx.com.

K.xprev()¶

previous items

For details, see q.xprev and xprev on code.kx.com.

K.xrank()¶

items assigned to buckets

For details, see q.xrank and xrank on code.kx.com.

namespace q¶

pyq.q¶

q.__call__(m=None, *args)¶

Execute q code.

When called without arguments in an interactive session, q() presents a q) prompt where user can interact with kdb+ using q language commands.

The first argument to that may be given to q() should be a string containing a q language expression. If that expression evaluates to a function, the arguments to this function can be provided as additional arguments to q().

For example, the following passes a list and a number to the q ? (find) function:

>>> q('?', [1, 2, 3], 2)
k('1')

Q functions¶

q.abs()¶

absolute value The abs function computes the absolute value of its argument. Null is returned if the argument is null.

>>> q.abs([-1, 0, 1, None])
k('1 0 1 0N')