通过 Python 在 q-lang 查询中转义字符

Question

我在对 kdb 服务器的查询中应用转义序列时遇到问题。

本机查询是：

select lo:min price, hi:max price by sym from trade where date = 2007.02.28, not cond like "*[BMPQTUWZ]*", corr <= 1

欢迎任何帮助。

我是用Python发送的，为了传递双引号我在query里放了\"for":

from qpython import qconnection
import pandas as pd
from datetime import datetime

query = 'select lo:min price, hi:max price by sym from trade where date = 2007.02.28, not cond like \"*[BMPQTUWZ]*\", corr <= 1'

#query = '\"2+2\"'


print('Attempt to open a connection...')

q = qconnection.QConnection(host=server, port=server_port, username=user, password=server_password, timeout=server_timeout, pandas = True)
q.open()
print('Connection established...')

print('Attempt to send the query', query)
df = pd.DataFrame(q.sendSync(query))
print('Query <<', query, '>> sent...')

“2+2”的输出和 'select lo:min price, hi:max price by sym from trade where date = 2007.02.28, not cond like \"[BMPQTUWZ]\", corr <= 1' 的输出如下所列。

PS G:\atom-projects\test> python.exe .\test-1.py
Attempt to open a connection...
Connection established...
Attempt to send the query "2+2"
Traceback (most recent call last):
  File ".\test-1.py", line 23, in <module>
    df = pd.DataFrame(q.sendSync(query))
  File "C:\Python38\lib\site-packages\pandas\core\frame.py", line 509, in __init__
    raise ValueError("DataFrame constructor not properly called!")
ValueError: DataFrame constructor not properly called!


PS G:\atom-projects\test> python.exe .\test-1.py
Attempt to open a connection...
Connection established...
Attempt to send the query select lo:min price, hi:max price by sym from trade where date = 2007.02.28, not cond like "*[BMPQTUWZ]*", corr <= 1
Traceback (most recent call last):
  File ".\test-1.py", line 23, in <module>
    df = pd.DataFrame(q.sendSync(query))
  File "C:\Python38\lib\site-packages\qpython\qconnection.py", line 303, in sendSync
    response = self.receive(data_only = False, **options)
  File "C:\Python38\lib\site-packages\qpython\qconnection.py", line 380, in receive
    result = self._reader.read(**self._options.union_dict(**options))
  File "C:\Python38\lib\site-packages\qpython\qreader.py", line 138, in read
    message = self.read_header(source)
  File "C:\Python38\lib\site-packages\qpython\qreader.py", line 158, in read_header
    header = self._read_bytes(8)
  File "C:\Python38\lib\site-packages\qpython\qreader.py", line 388, in _read_bytes
    data = self._stream.read(length)
  File "C:\Python38\lib\socket.py", line 669, in readinto
    return self._sock.recv_into(b)
socket.timeout: timed out

现在，我遇到了转义字符的问题。

如果我将查询发送到 kdb 服务器。

query = 'select lo:min price, hi:max price by sym from trade where date = 2007.02.28, corr <= 1'

查询已发送。但是当我添加 not cond like \"[BMPQTUWZ]\" 时，出现错误。

OS 和 Python 语言详细信息： Windows10，x64，Python3.8.1

Answer 1

你试过转义方括号吗？

查询='select lo:min price, hi:max price by sym from trade where date = 2007.02.28, not cond like \"\[BMPQTUWZ\]\", corr <= 1'

Answer 2

我想你想要运行像这样的东西：

...在 \"BMPQTUWZ\"

中没有条件

Answer 3

转义对我来说效果很好：

q)t:([]sym:100?`1;cond:100#`Buy`Sell`Example;corr:100?2f;price:100?100f)
q)t
sym cond    corr      price   
------------------------------
n   Buy     1.339583  82.48839
m   Sell    1.17743   95.01603
a   Example 1.135715  54.35053
o   Buy     0.7889166 29.12758
b   Sell    1.851226  45.29782
…

df = q.sendSync('select hi:max price, lo:min price, cond:first cond  by sym from t where not cond like \"[BS]*\"')

df
    hi  lo  cond
sym             
b'a'    64.230790   24.164567   b'Example' 
b'b'    60.669536   12.766243   b'Example'
b'c'    85.688555   79.785111   b'Example'
b'd'    83.056125   83.056125   b'Example' 
b'e'    73.149409   73.149409   b'Example'
b'f'    93.359214   36.638445   b'Example' 
...

'\"2+2\"' 失败，因为返回了 4 并且无法在 DataFrame 中显示。

您的 select 似乎因超时而失败。也许尝试增加你的时间。

另外，您希望通过 select 实现什么目标？我的例子不是 cond 以 B 或 S 开头的地方。所以只有 returns 例子。

如果 cond 是单个字符列而不是符号，Conor 上面的建议可能会更快更好。如果它是一个像我上面的符号列，带有整个单词。 Like/Regex必须使用。

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