We Keep Coding

Regex For Special Character (S with line on top)

I was trying to write regex in Python to replace all non-ascii with an underscore, but if one of the characters is "S̄" (an 'S' with a line on the top), it adds an extra 'S'... Is there a way to account for this character as well? I believe it's a valid utf-8 character, but not ascii
Here's there code:
import re
line = "ra*ndom wordS̄"
print(re.sub('[\W]', '_', line))
I would expect it to output:
ra_ndom_word_
But instead I get:
ra_ndom_wordS__

The reason Python works this way is that you are actually looking at two distinct characters; there's an S and then it's followed by a combining macron U+0304
In the general case, if you want to replace a sequence of combining characters and the base character with an underscore, try e.g.
import unicodedata
def cleanup(line):
cleaned = []
strip = False
for char in line:
if unicodedata.combining(char):
strip = True
continue
if strip:
cleaned.pop()
strip = False
if unicodedata.category(char) not in ("Ll", "Lu"):
char = "_"
cleaned.append(char)
return ''.join(cleaned)
By the by, \W does not need square brackets around it; it's already a regex character class.
Python's re module lacks support for important Unicode properties, though if you really want to use specifically a regex for this, the third-party regex library has proper support for Unicode categories.
"Ll" is lowercase alphabetics and "Lu" are uppercase. There are other Unicode L categories so maybe tweak this to suit your requirements (unicodedata.category(char).startswith("L") maybe?); see also https://www.fileformat.info/info/unicode/category/index.htm

You can use the following script to get the desired output:
import re
line="ra*ndom wordS̄"
print(re.sub('[^[-~]+]*','_',line))
Output
ra_ndom_word_
In this approach, it works with other non-ascii characters as well :
import re
line="ra*ndom ¡¢£Ä wordS̄. another non-ascii: Ä and Ï"
print(re.sub('[^[-~]+]*','_',line))
output:
ra_ndom_word_another_non_ascii_and_

remove special charecters in a string using python

I have a string = "msdjdgf(^&%*(Aroha Technologies&^$^&*^CHJdjg" with special characters.
what i am trying is to remove all special charecters in the string and then display the word 'Aroha Technologies'
i was able to do with hard coding using lstrip() function but can anyone help me out how can i display string 'Aroha Technologies' in a single line using regular expressions.
edit suggested:-
by using this lstrip() and rstrip() functions i was able to remove characters from the string.
str = "msdjdgf(^&%*(Aroha Technologies&^$^&*^CHJdjg"
str=str.lstrip('msdjdgf(^&%*(')
str=str.rstrip('&^$^&*^CHJdjg')

here, A bit more dirty approach
import re # A module in python for String matching/operations
a = "msdjdgf(^&%*(Aroha Technologies&^$^&*^CHJdjg"
stuff = re.findall('\W(\w+\s\w+)\W', a)
print(stuff[0]) # Aroha Technologies
hope this helps ;)

You don't provide a lot of information, so this may or may not be close to what you want:
import re
origstr = "msdjdgf(^&%(Aroha Technologies&^$^&^CHJdjg"
match = re.search("[A-Z][a-z]*(?: [A-Z][a-z]*)*", origstr)
if match:
newstr = match.group()
(looks for a series of capitalized words with spaces between them)

Regex End of Line and Specific Chracters

So I'm writing a Python program that reads lines of serial data, and compares them to a dictionary of line codes to figure out which specific lines are being transmitted. I am attempting to use a Regular Expression in order to filter out the extra garbage line serial read string has on it, but I'm having a bit of an issue.
Every single code in my dictionary looks like this: T12F8B0A22**F8. The asterisks are the two alpha numeric pieces that differentiate each string code.
This is what I have so far as my regex: '/^T12F8B0A22[A-Z0-9]{2}F8$/'
I am getting a few errors with this however. My first error, is that there are some characters are the end of the string I still need to get rid of, which is odd because I thought $/ denoted the end of the line in regex. However when I run my code through the debugger I notice that after running through the following code:
#regexString contains the serial read line data
regexString = re.sub('/^T12F8B0A22[A-Z0-9]{2}F8$/', '', regexString)
My string looks something like this: 'T12F8B0A2200F8\\r'
I need to get rid of the \\r.
If for some reason I can't get rid of this with regex, how in python do you send specific string character through an argument? In this case I suppose it would be length - 3?

Your problem is threefold:
1) your string contains extra \r (Carriage Return character) before \n (New Line character); this is common in Windows and in network communication protocols; it is probably best to remove any trailing whitespace from your string:
regexString = regexString.rstrip()
2) as mentioned by Wiktor Stribiżew, your regexp is unnecessarily surrounded with / characters - some languages, like Perl, define regexp as a string delimited by / characters, but Python is not one of them;
3) your instruction using re.sub is actually replacing the matching part of regexString with an empty string - I believe this is the exact opposite of what you want (you want to keep the match and remove everything else, right?); that's why fixing the regexp makes things "even worse".
To summarize, I think you should use this instead of your current code:
m = re.match('T12F8B0A22[A-Z0-9]{2}F8', regexString)
regexString = m.group(0)

There are several ways to get rid of the "\r", but first a little analysis of your code :
1. the special charakter for the end is just '$' not '$\' in python.
2. re.sub will substitute the matched pattern with a string ( '' in your case) wich would substitute the string you want to get with an empty string and you are left with the //r
possible solutions:
use simple replace:
regexString.replace('\\r','')
if you want to stick to regex the approach is the same
pattern = '\\\\r'
match = re.sub(pattern, '',regexString)
2.2 if you want the acces the different groubs use re.search
match = re.search('(^T12F8B0A22[A-Z0-9]{2}F8)(.*)',regexString)
match.group(1) # will give you the T12...
match.groupe(2) # gives you the \\r

Just match what you want to find. Couple of examples:
import re
data = '''lots of
otherT12F8B0A2212F8garbage
T12F8B0A2234F8around
T12F8B0A22ABF8the
stringsT12F8B0A22CDF8
'''
print(re.findall('T12F8B0A22..F8',data))
['T12F8B0A2212F8', 'T12F8B0A2234F8', 'T12F8B0A22ABF8', 'T12F8B0A22CDF8']
m = re.search('T12F8B0A22..F8',data)
if m:
print(m.group(0))
T12F8B0A2212F8

Python regular expression with string in it

I would like to match a string with something like:
re.match(r'<some_match_symbols><my_match><some_other_match_symbols>', mystring)
where mymatch is a string I would like it to find. The problem is that it may be different from time to time, and it is stored in a variable. Would it be possible to add one variable to a regex?

Nothing prevents you from simply doing this:
re.match('<some_match_symbols>' + '<my_match>' + '<some_other_match_symbols>', mystring)
Regular expressions are nothing else than a string containing some special characters, specific to the regular expression syntax. But they are still strings, so you can do whatever you are used to do with strings.
The r'…' syntax is btw. a raw string syntax which basically just prevents any escape sequences inside the string from being evaluated. So r'\n' will be the same as '\\n', a string containing a backslash and an n; while '\n' contain a line break.

import re
url = "www.dupe.com"
expression = re.compile('<p>%s</p>'%url)
result = expression.match("<p>www.dupe.com</p>BBB")
if result:
print result.start(), result.end()

The r'' notation is for constants. Use the re library to compile from variables.

Regular Expression Not matching the value

I have a file saving IP addresses to names in format
<<%#$192.168.8.40$#% %##Name_of_person##% >>
I read This file and now want to extract the list using pythons regular expressions
list=re.findall("<<%#$(\S+)$#%\s%##(\w+\s*\w*)##%\s>>",ace)
print list
But the list is always an empty list..
can anyone tell me where is the mistake in the regular expression
edit-ace is the variable saving the contents read from the file

$ is a special character in regular expressions, meaning "end of line" (or "end of string", depending on the flavour). Your regex has other characters following the $, and as such only matches strings that have those characters after the end, which is impossible.
You will need to escape the $, like so: \$
I would suggest the following regular expression (formatted as a raw string since you are using Python):
r"<<%#\$([^$]+)\$#%\s%##([^#]+)##%\s>>"
That is, <<%#$, then one or more non-$ characters, $#%, a whitespace character, %##, one or more non-# characters, ##%, whitespace, >>.

Something like:
text = '<<%#$192.168.8.40$#% %##Name_of_person##% >>'
ip, name = [el[1] for el in re.findall(r'%#(.)(.+?)\1#%', text)]
If you can get any with just splitting on '#' and '$' then...
from itertools import itemgetter
ip, name = itemgetter(1, 3)(re.split(r'[#\$]', text))
You could also just use built-in string functions:
tmp = text.split('$')
ip, name = tmp[1], tmp[2].split('#')[1]

u use a invalid regex pattern.
you may use
r"<\%#\$(\S+)\$#\%\s\%##(\w+\s*\w*)##\%\s>>" replace
"<<%#$(\S+)$#%\s%##(\w+\s*\w*)##%\s>>" in fandall method
good luck~!