Develop Reference

repr() without leading and trailing quote?

Need string to display \n in printed output without trailing + leading '. Currently using repr on the input (opening + reading .txt) so I'm wondering what's the best way to remove the 's for proper indexing/search?
repr('s')[1:-1]
repr('s').strip("'")
Unfortunately some characters are being escaped which I don't want escaped using repr such as '.

You don't say why you would want to do this, but I'm guessing you plan to store the string in a database or a .csv file or something, and you don't want non-printing characters like linefeeds in your data because they can make other tools like SQL interpreters misbehave.
If this is a correct guess, don't use repr() because it will escape characters that I imagine you don't want escaped, like quotes and backslashes. Instead, decide what non-printing characters you want to quote (I think the only likely ones are \n and \t) and substitute them yourself.
fixed_s = s.replace("\n",r"\n").replace("\t",r"\t")
But if you are just using the string as an ordinary Python dictionary key, don't manipulate it, use it as-is.

You're using repr() prematurely. It's meant to be used on output, not input.
Add repr(string) to your print statements and remove it from the input.

python regular expression not matching file contents with re.match and re.MULTILINE flag

I'm reading in a file and storing its contents as a multiline string. Then I loop through some values I get from a django query to run regexes based on the query results values. My regex seems like it should be working, and works if I copy the values returned by the query, but for some reason isn't matching when all the parts are working together that ends like this
My code is:
with open("/path_to_my_file") as myfile:
data=myfile.read()
#read saved settings then write/overwrite them into the config
items = MyModel.objects.filter(some_id="s100009")
for item in items:
regexString = "^\s*"+item.feature_key+":"
print regexString #to verify its what I want it to be, ie debug
pq = re.compile(regexString, re.M)
if pq.match(data):
#do stuff
So basically my problem is that the regex isn't matching. When I copy the file contents into a big old string, and copy the value(s) printed by the print regexString line, it does match, so I'm thinking theres some esoteric python/django thing going on (or maybe not so esoteric as python isnt my first language).
And for examples sake, the output of print regexString is :
^\s*productDetailOn:
File contents:
productDetailOn:true,
allOff:false,
trendingWidgetOn:true,
trendingWallOn:true,
searchResultOn:false,
bannersOn:true,
homeWidgetOn:true,
}
Running Python 2.7. Also, dumped the types of both item.feature and data, and both were unicode. Not sure if that matters? Anyway, I'm starting to hit my head off the desk after working this for a couple hours, so any help is appreciated. Cheers!

According to documentation, re.match never allows searching at the beginning of a line:
Note that even in MULTILINE mode, re.match() will only match at the beginning of the string and not at the beginning of each line.
You need to use a re.search:
regexString = r"^\s*"+item.feature_key+":"
pq = re.compile(regexString, re.M)
if pq.search(data):
A small note on the raw string (r"^\s+"): in this case, it is equivalent to "\s+" because there is no \s escape sequence (like \r or \n), thus, Python treats it as a raw string literal. Still, it is safer to always declare regex patterns with raw string literals in Python (and with corresponding notations in other languages, too).

Accommodate two types of quotes in a regex

I am using a regex to replace quotes within in an input string. My data contains two 'types' of quotes -
" and “
There's a very subtle difference between the two. Currently, I am explicitly mentioning both these types in my regex
\"*\“*
I am afraid though that in future data I may get a different 'type' of quote on which my regex may fail. How many different types of quotes exist? Is there way to normalize these to just one type so that my regex won't break for unseen data?
Edit -
My input data consists of HTML files and I am escaping HTML entities and URLs to ASCII
escaped_line = HTMLParser.HTMLParser().unescape(urllib.unquote(line.decode('ascii','ignore')))
where line specifies each line in the HTML file. I need to 'ignore' the ASCII as all files in my database don't have the same encoding and I don't know the encoding prior to reading the file.
Edit2
I am unable to do so using replace function. I tried replace('"','') but it doesn't replace the other type of quote '“'. If I add it in another replace function it throws me NON-ASCII character error.
Condition
No external libraries allowed, only native python libraries could be used.

I don't think there is a "quotation marks" character class in Python's regex implementation so you'll have to do the matching yourself.
You could keep a list of common quotation mark unicode characters (here's a list for a good start) and build the part of regex that matches quotation marks programmatically.

I can only help you with the original question about quotations marks. As it turns out, Unicode defines many properties per character and these are all available though the Unicode Character Database. "Quotation mark" is one of these properties.
How many different types of quotes exist?
29, according to Unicode, see below.
The Unicode standard brings us a definitive text file on Unicode properties, PropList.txt, among which a list of quotation marks. Since Python does not support all Unicode properties in regular expressions, you cannot currently use \p{QuotationMark}. However, it's trivial to create a regular expression character class:
// placed on multiple lines for readability, remove spaces
// and then place in your regex in place of the current quotes
[\u0022 \u0027 \u00AB \u00BB
\u2018 \u2019 \u201A \u201B
\u201C \u201D \u201E \u201F
\u2039 \u203A \u300C \u300D
\u300E \u300F \u301D \u301E
\u301F \uFE41 \uFE42 \uFE43
\uFE44 \uFF02 \uFF07 \uFF62
\uFF63]
As "tchrist" pointed out above, you can save yourself the trouble by using Matthew Barnett's regex library which supports \p{QuotationMark}.

Turns out there's a much easier way to do this. Just append the literal 'u' in front of your regex you write in python.
regexp = ru'\"*\“*'
Make sure you use the re.UNICODE flag when you want to compile/search/match your regex to your string.
re.findall(regexp, string, re.UNICODE)
Don't forget to include the
#!/usr/bin/python
# -*- coding:utf-8 -*-
at the start of the source file to make sure unicode strings can be written in your source file.

dealing with \n characters at end of multiline string in python

I have been using python with regex to clean up a text file. I have been using the following method and it has generally been working:
mystring = compiledRegex.sub("replacement",mystring)
The string in question is an entire text file that includes many embedded newlines. Some of the compiled regex's cover multiple lines using the re.DOTALL option. If the last character in the compiled regex is a \n the above command will substitute all matches of the regex except the match that ends with the final newline at the end of the string. In fact, I have had several other no doubt related problems dealing with newlines and multiple newlines when they appear at the very end of the string. Can anyone give me a pointer as to what is going on here? Thanks in advance.

If i correctly undestood you and all that you need is to get a text without newline at the end of the each line and then iterate over this text in order to find a required word than you can try to use the following:
data = (line for line in text.split('\n') if line.strip())# gives you all non empty lines without '\n'at the end
Now you can either search/replace any text you need using list slicing or regex functionality.
Or you can use replace in order to replace all '\n' to whenever you want:
text.replace('\n', '')

My bet is that your file does not end with a newline...
>>> content = open('foo').read()
>>> print content
TOTAL:.?C2
abcTOTAL:AC2
defTOTAL:C2
>>> content
'TOTAL:.?C2\nabcTOTAL:AC2\ndefTOTAL:C2'
...so the last line does not match the regex:
>>> regex = re.compile('TOTAL:.*?C2\n', re.DOTALL)
>>> regex.sub("XXX", content)
'XXXabcXXXdefTOTAL:C2'
If that is the case, the solution is simple: just match either a newline or the end of the file (with $):
>>> regex = re.compile('TOTAL:.*?C2(\n|$)', re.DOTALL)
>>> regex.sub("XXX", content)
'XXXabcXXXdefXXX'

I can't get a good handle on what is going on from your explanation but you may be able to fix it by replacing all multiple newlines with a single newline as you read in the file. Another option might be to just trim() the regex removing the \n at the end unless you need it for something.

Is the question mark to prevent the regex matching more than one iine at a time? If so then you probably want to be using the MULTILINE flag instead of DOTALL flag. The ^ sign will now match just after a new line or the beginning of a string and the $ sign will now match just before a newline character or the end of a string.
eg.
regex = re.compile('^TOTAL:.*$', re.MULTILINE)
content = regex.sub('', content)
However, this still leaves with the problem of empty lines. But why not just run one additional regex at the end that removes blank lines.
regex = re.compile('\n{2,}')
content = regex.sub('\n', content)

Extra characters Extracted with XPath and Python (html)

I have been using XPath with scrapy to extract text from html tags online, but when I do I get extra characters attached. An example is trying to extract a number, like "204" from a <td> tag and getting [u'204']. In some cases its much worse. For instance trying to extract "1 - Mathoverflow" and instead getting [u'\r\n\t\t 1 \u2013 MathOverflow\r\n\t\t ']. Is there a way to prevent this, or trim the strings so that the extra characters arent a part of the string? (using items to store the data). It looks like it has something to do with formatting, so how do I get xpath to not pick up that stuff?

What does the line of code look like that returns [u'204']? It looks like what is being returned is a Python list containing a unicode string with the value you want. Nothing wront there--just subscript. As for the carriage returns, linefeeds and tabs, as Wai Yip Tung just answered, strip will take them out.
Probably
my_answer = item1['Title'][0].strip()
Or if you are expecting several matches
for ans_i in item1['Title']:
do_something_with( ans_i.strip() )

The standard XPath function normalize-space() has exactly the wanted effect.
It deletes the leading and trailing wite space and replaces any inner whitespace with just one space.
So, you could use:
normalize-space(someExpression)

Use strip() to remove the leading and trailing white spaces.
>>> u'\r\n\t\t 1 \u2013 MathOverflow\r\n\t\t '.strip()
u'1 \u2013 MathOverflow'