Project WowNow

Friday 13 September 2019

Python: Which is Quicker to Search a String, Find or In?

There are many ways to do the same task in Python, as with most things. Here I wanted to know which was quicker to see if a string contained a space:

if x.find(' ') != -1:

if ' ' in x:

So a little test...

import datetime x = 'abc def' r = 100000000 def test_a(): if x.find(' ') != -1: pass def test_b(): if ' ' in x: pass start = datetime.datetime.now() for a in range(0, r): test_a() print('Test A: ' + str(datetime.datetime.now()-start)) start = datetime.datetime.now() for a in range(0, r): test_b() print('Test B: ' + str(datetime.datetime.now()-start))

... found that ...

Test A: 0:00:27.240583 Test B: 0:00:13.469368

"in" being the clear winner here and no real surprise as "find" has to do more work to return the character's position.

Thursday 21 February 2019

HTML Character Codes

There are several websites which list the popular HTML Character Codes but if you need to view them all, this short HTML Javascript snippet will list all the numbered codes in your browser.

<html> <head> <style> table { border-collapse: collapse; } th { width: 3em; padding: 0.6em; background: lightgray; color: darkslategray; font-size: 0.6em; } td { width: 3em; padding: 0.6em; display: inline-block; border: 1px solid lightgray; text-align: center; } </style> </head> <body> <table> <script> for (i=0; i<80000; i++) { document.write('<tr><th>&#' + i + ';</th><td> &#' + i + '; </td></tr>'); } </script> </table> </body> </html>

✋

Tuesday 22 January 2019

Adding Floating Point Numbers in Python

I've recently been doing some work in Python and noticed that it can't add floating point numbers correctly! I Googled it and found that this isn't a bug, it's expected because the C code underneath converts the floating point into a fraction to add the numbers and not all numbers can be converted to fractions and vice-versa!!

It may be expected but it is definitely in no way correct.

With my limited knowledge I've created this function to convert the floating point numbers to decimals, perform the addition, then convert back to floating point.

def add_floats(v): multiplier = 1 for i in v: multiplier = max(len(str(i)) - str(i).find('.'), multiplier) multiplier = 10**multiplier total = 0 for i in v: total += (i * multiplier) total = total / multiplier return total x = float('1.41') y = float('1.4') z = x+y print(x+y) print(add_floats([x, y]))

Output:

2.8099999999999996 2.81

My Python knowledge is limited, so if anyone wishes to improve this, please let me know.

Monday 7 March 2016

Installing SQLPlus on Windows 10 and "MSVCP100.dll Missing"

Firstly to install SQLPlus on Windows 10 I downloaded two packages from Oracle.

http://www.oracle.com/technetwork/topics/winx64soft-089540.html

The first "Instant Client Package - Basic Lite" has the main connection packages.

The second "Instant Client Package - SQL*Plus" has the SQLPlus elements.

Unzip these to a folder. I used "C:\Oracle\instantclient_12_1".

I then tried to run SQLPLUS.exe and got the error "The program can't start because MSVCR100.dll is missing from your computer. try reinstalling the program to fix this problem"

A quick Google search found that this is some kind of C++ library. I downloaded the necessary files from http://www.microsoft.com/en-us/download/details.aspx?id=14632.

I dropped my tnsnames.ora file into the instant client directory, ran SQLPlus again and voila.

SQL>

Tuesday 26 January 2016

Oracle Flashback Source PLSQL Code

Aaaaarrgh! Just modified some PLSQL in the database and lost what the previous version, with lots of cool stuff in I did this morning! :-(

Luckily, using the AS OF flashback clause I can rewind time and get the code back.
(NB: To get this to work I had to SSH to the server and connect as SYS via SqlPlus)

SELECT text FROM sys.dba_source AS OF TIMESTAMP TO_TIMESTAMP('2016-01-26 12:34:00', 'YYYY-MM-DD HH24:MI:SS') WHERE owner = 'schema' AND name = 'object name' AND type = 'PACKAGE BODY' ORDER BY line ;

Change as required and carry on.
:-)

Tuesday 24 November 2015

Oracle SQL Tuning: Quick Test Template

Sometime using explain plan doesn't clearly give a answer to which way to write a query. This template allows a query to be run several times to give a idea of which way is faster.

BEGIN FOR a IN 1..1000 LOOP FOR b IN ( ... paste query here ... ) LOOP NULL; END LOOP; END LOOP; END; /

Done.

Friday 24 April 2015

Remove Oracle Job Process

Trying to kill a database job can be frustrating sometimes and they just won't die if you don;t do it right, especially if the job is owned by a different user.

So first identify the job you are looking for using:

SELECT * FROM dba_jobs ;

Then use DBMS_IJOB to remove the job. Use the value from the JOB column above as the parameter value.

EXEC SYS.DBMS_IJOB.REMOVE(?);

I'm using Oracle 11 but I believe that, although this is undocumented, this has been around for several years now.

Removed.