The other day I was reading an August issue of my favorite magazine, Linux Journal. On page 17 there is a list of the ten most popular articles off all-time on LinuxJournal.com. At the #1 is article written by Eric Raymond, titled Why Python?.

I was pleasantly surprised. It’s precisely this article that ended my ultimate quest for scripting language back in 2004. Frankly, I was sick of Microsoft WSH that I was using back then; besides I needed scripting language that could run equally well on Windows & Linux (support for other major flavors of Unix would be a plus) and with solid support for various text processing/parsing functions, that could allow me to “glue” together some tasks related to ETL (mostly DBA stuff).

I spent considerable amount of the first half of year 2004 evaluating various scripting languages — somehow skipping python at first (can’t remember why I dismissed python so quickly). Since I knew that Perl has strong parsing capabilities (regular expressions etc.), it was this language that I used to “benchmark” all others against.

Perl could probably pass my evaluation if only the written code would not look so wacky (with all due respect to Perl community) – then one day Google returned link to the article written by Eric Raymond, “Why Python?”. It was revealing experience reading this article. I downloaded and installed python immediately after I finished with the article, browsed the manuals and when I saw some code examples, I thought: what a beauty (sorry if it sounds too geeky)! It was love at first sight, I knew I was hooked for life. Since then, I never looked back, python is my favorite scripting language. The only thing I really regret is that I didn’t “find” the python earlier in my career. What a pity!

Here I’ll try to maintain a list of articles published on OTN about python & Oracle:

• Python cx_Oracle 5.0 New Features Overview
• High Concurrency with Python and Oracle Database
• Python Data Persistence with Oracle Database
• Using Python with TurboGears
• Mastering Oracle+Python, Part 1: Querying Best Practices
• Mastering Oracle+Python, Part 2: Working with Times and Dates
• Mastering Oracle+Python, Part 3: Data Parsing
• Mastering Oracle+Python, Part 4: Transactions and large objects
• Mastering Oracle+Python, Part 5: Stored Procedures, Programming Python
• Build a Rapid Web Development Environment for Python Server Pages and Oracle
• Wrapping Your Brain Around Oracle + Python
• Using Python With Oracle 11g

I wrote a simple python script for converting xml export files generated by SQL Developer to csv format.

Let’s first see what is the output from SQL Developer. Export file of the Oracle table EMP generated by SQL Developer looks like this:

<?xml version='1.0'  encoding='Cp1250' ?>
<RESULTS>
	<ROW>
		<COLUMN NAME="COMM"><![CDATA[]]></COLUMN>
		<COLUMN NAME="DEPTNO"><![CDATA[20]]></COLUMN>
		<COLUMN NAME="EMPNO"><![CDATA[7369]]></COLUMN>
		<COLUMN NAME="ENAME"><![CDATA[SMITH]]></COLUMN>
		<COLUMN NAME="HIREDATE"><![CDATA[17.12.1980]]></COLUMN>
		<COLUMN NAME="JOB"><![CDATA[CLERK]]></COLUMN>
		<COLUMN NAME="MGR"><![CDATA[7902]]></COLUMN>
		<COLUMN NAME="SAL"><![CDATA[800]]></COLUMN>
	</ROW>
	<ROW>
		<COLUMN NAME="COMM"><![CDATA[300]]></COLUMN>
		<COLUMN NAME="DEPTNO"><![CDATA[30]]></COLUMN>
		<COLUMN NAME="EMPNO"><![CDATA[7499]]></COLUMN>
		<COLUMN NAME="ENAME"><![CDATA[ALLEN]]></COLUMN>
		<COLUMN NAME="HIREDATE"><![CDATA[20.02.1981]]></COLUMN>
		<COLUMN NAME="JOB"><![CDATA[SALESMAN]]></COLUMN>
		<COLUMN NAME="MGR"><![CDATA[7698]]></COLUMN>
		<COLUMN NAME="SAL"><![CDATA[1600]]></COLUMN>
	</ROW>
	<ROW>
		<COLUMN NAME="COMM"><![CDATA[500]]></COLUMN>
		<COLUMN NAME="DEPTNO"><![CDATA[30]]></COLUMN>
		<COLUMN NAME="EMPNO"><![CDATA[7521]]></COLUMN>
		<COLUMN NAME="ENAME"><![CDATA[WARD]]></COLUMN>
		<COLUMN NAME="HIREDATE"><![CDATA[22.02.1981]]></COLUMN>
		<COLUMN NAME="JOB"><![CDATA[SALESMAN]]></COLUMN>
		<COLUMN NAME="MGR"><![CDATA[7698]]></COLUMN>
		<COLUMN NAME="SAL"><![CDATA[1250]]></COLUMN>
	</ROW>
</RESULTS>

And my goal was to convert xml file to csv format:

COMM;DEPTNO;EMPNO;ENAME;HIREDATE;JOB;MGR;SAL;
;20;7369;SMITH;17.12.1980;CLERK;7902;800;
300;30;7499;ALLEN;20.02.1981;SALESMAN;7698;1600;
500;30;7521;WARD;22.02.1981;SALESMAN;7698;1250;


In this “exercise” I decided to use minidom for xml parsing which is quite easy to code with, but at the same time is suitable only for small xml files, such as exports of database code books. Perhaps I’ll publish similar python script, where I’ll parse xml with sax module.

# -*- coding: cp1250 -*-
# xml2csv.py -- AlesK, 2009
#
# Purpose:
# simple python code snippet that shows how to use python minidom module
# to convert export file produced by Oracle SQL Developer (Table->Export->to xml)
# to csv format. Note that minidom (DOM) as such is suitable for parsing
# small xml files, such as database codebooks!
#
# Note: Script doesn't even try to do any error handling at all and 
# as such is far away from being anything more than a simple demo.
#
# Example:
# cmd> python xml2csv.py emp.xml > emp.csv
#
import sys
import xml.dom.minidom

doc = xml.dom.minidom.parse(sys.argv[1])

# if encoding is not explicitly declared in xml header then 
# I'm assuming Cp1250 for the output file
if doc.encoding:
    encode = doc.encoding
else:
    # Cp1250 is my personal preference if encoding is not
    # specified in xml header
    encode = 'Cp1250'

# fields delimiter    
csv = ';'    

# during the pass of the first ROW collect
# column names (for csv file header)
firstRowPass = True
header = ''

for row in doc.getElementsByTagName("ROW"):
    row_data = ''
    for column in row.getElementsByTagName("COLUMN"):
        for column_value in column.childNodes:
            row_data += column_value.data
        row_data += csv
        if firstRowPass:
            header += column.getAttribute('NAME') + csv
    if firstRowPass:
        print header.encode(encode)
        firstRowPass = False
    print row_data.encode(encode)

doc.unlink()
#
# End xml2csv.py
#

This is just a short memo about handy python module, called SimpleHTTPServer. Sometimes I need a way to quickly share some files with co-worker, without copying and/or creating shared folder. All I need is a quick way to allow someone read-only access to a specific folder. Let’s say that security is of no concern to me in such situation, since I’m talking about giving access to publicly available files anyway, such as drivers, installation files etc.

One neat way is to use python module SimpleHTTPServer.

All that is needed is this one-liner:

T:\Download>python -m SimpleHTTPServer
Serving HTTP on 0.0.0.0 port 8000 ...
alesk.domain.com - - [02/Feb/2009 18:13:49] "GET / HTTP/1.1" 200 -
alesk.domain.com - - [02/Feb/2009 18:14:03] "GET /Accton/ HTTP/1.1" 200 -
alesk.domain.com - - [02/Feb/2009 18:14:13] "GET /Accton/EN1207DTXv133.zip HTTP/1.1" 200 -

And the files will be available at http://yourhost:8000. Simply close the console after you’re done and http server will stop serving.

Last final note: be extremely careful that you cd to directory of interest, thus limiting access to only a particular directory. Remember that anyone with network access to your machine can access those files without authentication.

Guido van Rossum recently started to blog about history of Python. Guido will write a series of articles, explaining how python was developed in the last 19 years (yes, time really flies – believe it or not, python is 19 years old). Python is today one of the most popular dynamic programming languages in the field with steadily growing community of new programmers. I’m looking forward to read the series of articles at History of Python.