taT4Py | Recursively Search Regex Patterns

I have mainly used python for parsing text, validation and transforming as needed. If it was done using shell script, I would end up writing variety of regular expression to play around.

Getting Started

Well, python is no different and in order to cook up regular expressions, one must import re (module) and get started.

import re

So far, I have been able to use the patterns exactly the same way as I would with grep or sed. Usually, I end up writing multiple search patterns, as the script evolves. While using python, I find it intuitive to create dictionary of compiled search patterns (RegexObject), I wrote to style unified differences, as follows.

regexDict = {
    'HEADER': re.compile("^@@ ([+-][0-9]+(,[0-9]+)? ?){1,2} @@$"),
    'ADD':    re.compile("^\+"),
    'DEL':    re.compile("^\-")
}

Search Recursively

Looking at the above dictionary, there are only 3 key-value pairs, so writing if-else construct would be easy. Let say, such a dictionary is dynamically created and can have any number of key-value pairs.

All you need to figure out, whether data matches particular search pattern or not. If yes, print the data, or transform the data, etc. In this post, we will go one step further and redesign the if-else construct used to style unified differences, as follows.

with open(inputFile, 'r') as fileObj:

    ### Using Slice To Ignore First 2 Lines
    for line in fileObj.read().splitlines()[2:]:

        fn__recurSearch(regexDict.keys(), line)

The for-statement invokes function with two arguments, first one of the type – iterator and the other one – string. Let us look at the function definition below;

def fn__recurSearch(iterator, data):

    if not iterator:
        print data
        return

    key = iterator.pop(0)

    matchObj = regexDict[key].search(data)

    if not matchObj:
        fn__recurSearch(iterator, data)
        return

    print data

Steps Ahead

The function looks straight forward, however this would simply dump the file as is on the STDOUT. If you have paid attention, you will notice, we have not added logic to style unified differences !!

Well, that’s an exercise left it for you, otherwise I will try to cover next time.

code4Py | Style Unified Differences

As per recently created page, the following diff command output representing unified differences, needed to be styled;

[vagrant@localhost python]$ diff -u A B
--- A   2014-08-20 20:13:30.315009258 +0000
+++ B   2014-08-20 20:13:39.021009349 +0000
@@ -1,6 +1,9 @@
+typeset -i sum=0
+
 while read num
 do
   printf "%d " ${num}
+  sum=sum+${num}
 done <<EOF
 1
 2
@@ -9,5 +12,4 @@
 5
 EOF

-echo
-
+echo; echo "Sum: ${sum}"
[vagrant@localhost python]$

Source Code (GitHub Gist)
I have completed writing python script that will generate HTML output as follows.

<tr>
  <td>
    <span style='color: green'>typeset -i sum=0</span><br />
    <span style='color: green'></span><br />
    while read num<br />
    do<br />
      printf "%d " ${num}<br />
    <span style='color: green'>  sum=sum+${num}</span><br />
    done <<EOF<br />
    1<br />
    2
  </td>
</tr>
<tr>
  <td>
    5<br />
    EOF<br />
    <br />
    <span style='color: red'>echo </span><br />
    <span style='color: red'></span><br />
    <span style='color: green'>echo; echo "Sum: ${sum}"</span>
  </td>
</tr>

Style Output
This output tabulates the differences in N-row(s) and single-column format, if properly embedded into table element of HTML document, which could then be rendered by web browser based on CSS properties (if defined).

code4Py | Style Context Differences

As per recently created page, the following diff command output representing context differences, needed to be styled;

[vagrant@localhost python]$ diff -c A B
*** A   2014-08-20 20:13:30.315009258 +0000
--- B   2014-08-20 20:13:39.021009349 +0000
***************
*** 1,6 ****
--- 1,9 ----
+ typeset -i sum=0
+
  while read num
  do
    printf "%d " ${num}
+   sum=sum+${num}
  done <<EOF
  1
  2
***************
*** 9,13 ****
  5
  EOF

! echo
!
--- 12,15 ----
  5
  EOF

! echo; echo "Sum: ${sum}"
[vagrant@localhost python]$

Source Code (GitHub Gist)
I have completed writing python script that will generate HTML output as follows.

<tr>
  <td>

  </td>
  <td>
    <span style='color: green'> typeset -i sum=0</span><br />
    <span style='color: green'> </span><br />
     while read num<br />
     do<br />
       printf "%d " ${num}<br />
    <span style='color: green'>   sum=sum+${num}</span><br />
     done <<EOF<br />
     1<br />
     2
  </td>
</tr>
<tr>
  <td>
     5<br />
     EOF<br />
     <br />
    <span style='color: blue'> echo </span><br />
    <span style='color: blue'> </span>
  </td>
  <td>
     5<br />
     EOF<br />
     <br />
    <span style='color: blue'> echo; echo "Sum: ${sum}"</span>
  </td>
</tr>

Style Output
This output tabulates the differences in N-row(s) and 2-column(s) format, if properly embedded into table element of HTML document, which could then be rendered by web browser based on CSS properties (if defined).

taT4JS | Handle Select Menu Inter-Dependencies

Recently, while prototyping intranet website I came across scenario, wherein the top section of the web page is required to have two drop-down lists, i.e. select tags, which would have inter-dependency.

Let say, the web page is divided into 3 sections;

  • #top, having drop-down lists,
  • #middle, which will reload asynchronously based on the context set by drop-down lists,
  • #bottom, like page footer.

The first drop-down list is populated with names of programming languages and second drop-down list is populated with list of categories like Tutorials, Tips and Tricks, FAQs, etc.

Playing Tricks

$('#selMenu_typeOne').change(function() {
        $('#selMenu_typeTwo').trigger('change');
});
$('#selMenu_typeTwo').change(function() { 
        //execute some function, or 
        //do some global variable assignment operations
});

As per the above snippet, as soon as user selects an item from #selMenu_typeOne drop-down list, it would automatically trigger the similar event for the #selMenu_typeTwo drop-down list.

To implement the async functionality, I used $.getJSON() functions to read necessary information from JSON file, whose naming is dependent on the items selected from drop-down lists and format it into tables, lists, etc.

Tips to Remember

Let say, user selected Java from first list, which resets the second list to select Tutorials by default. This would, in turn cause #middle section to reload async accordingly. This enables user to change the selection in any of the drop-down lists to view data asynchronously with ease.

taT4Py | Convert AutoSys Job Attributes into Python Dictionary

If you ever look at the definition of specific AutoSys Job, you would find that it contains attribute-value pairs (line-by-line), delimited by colon ‘:’ I thought it would be cool to parse the job definition, by creating python dictionary using the attribute-value pairs.

Let us take a look at sample job definition;

$> cat sample_jil
insert_job: A0001
command: echo "Hi"
condition: s(B0001, 03\:00) & v(SRVR) = "UP"
std_out_file: >/home/nvarun/outfile
std_err_file: >/home/nvarun/errfile
group: NV
$>

Getting Started

To convert this into Python Dictionary, execute the following command;

$> sed "s/^\([^:]*\):\(.*\)$/'\1':'\2'/" sample_jil > sample_pydict
$> cat sample_pydict
'insert_job':' A0001'
'command':' echo "Hi"'
'condition':' s(B0001, 03\:00) & v(SRVR) = "UP"'
'std_out_file':' >/home/nvarun/outfile'
'std_err_file':' >/home/nvarun/errfile'
'group':' NV'
$>

We are half-way through, to complete the conversion, write following steps in python script and populate dictionary as follows;

import string
jobDefn = {}
with open('sample_pydict', 'r') as f:
    for line in f.read().splitlines():
        colon = string.find(line, ':')
        key = string.replace(line[:colon], "'", "")
        val = line[colon+1:].strip()
        jobDefn[key] = val
print jobDefn

Summary

  1. Using f.read() reads the input file at one go and invoking splitlines() splits the input into list of several lines, resulting in creating an iterator.
  2. The for-statement iterates over each line, wherein position of first occurrence of colon is found and used for extracting key, value based on slicing.
  3. At the end of the loop, the dictionary object jobDefn is printed.

Hope this helps.