I want to be able to match and parse some parameters read from a file such as :
"type:int,register_id:15,value:123456"
"type:int,register_id:16,value:-456789"
"type:double,register_id:17,value:123.456"
"type:double,register_id:18,value:-456.789"
"type:bool,register_id:19,value:true"
"type:bool,register_id:20,value:false"
"type:string,register_id:17,value:Test Set Data Register"
I've come up with the following Regex expression :
(^(type:)\b(bool|int|double|string)\b,(\bregister_id:\b)([1-9][0-9]),(\bvalue:\b)(.)$)
but I have issues where there are negative floats or ints, I can't get the hyphen sorted properly ...
Can someone point me in the right direction ?
https://regex101.com/r/WhXmBE/3
Thanks !
Tried [\s\S] but it reads everything, tried -? as well
Given your example, this seems to work:
(^(type:)(bool|int|double|string),(register_id:)([1-9][0-9]*),(value:)(.*)$)
At least from the example, I didn't see why the \b are necessary. Apologies if I missed something.
Looking at what you try to achieve, I would actually consider moving away from regexes, as regexes by themselves add complexity. You will likely have an easier life if you approach it like this:
Split the line by "," to get the key value pairs
Split each key value pair by the first ":" to split key and value
Validate that all keys are present and that every value matches the format for the key (e.g. if the type is bool then the value should parse to a bool)
You can easily adjust every step to e.g. trim whitespaces.
Edit: Fixed typo
I am working with a messy manually maintained "database" that has a column containing a string with name,value pairs. I am trying to parse the entire column with regexp to pull out the values. The column is huge (>100,000 entries). As a proxy for my actual data, let's use this code:
line1={'''thing1'': ''-583'', ''thing2'': ''245'', ''thing3'': ''246'', ''morestuff'':, '''''};
line2={'''thing1'': ''617'', ''thing2'': ''239'', ''morestuff'':, '''''};
line3={'''thing1'': ''unexpected_string(with)parens5'', ''thing2'': 245, ''thing3'':''246'', ''morestuff'':, '''''};
mycell=vertcat(line1,line2,line3);
This captures the general issues encountered in the database. I want to extract what thing1, thing2, and thing3 are in each line using cellfun to output a scalar cell array. They should normally be 3 digit numbers, but sometimes they have an unexpected form. Sometimes thing3 is completely missing, without the name even showing up in the line. Sometimes there are minor formatting inconsistencies, like single quotes missing around the value, spaces missing, or dashes showing up in front of the three digit value. I have managed to handle all of these, except for the case where thing3 is completely missing.
My general approach has been to use expressions like this:
expr1='(?<=thing1''):\s?''?-?([\w\d().]*?)''?,';
expr2='(?<=thing2''):\s?''?-?([\w\d().]*?)''?,';
expr3='(?<=thing3''):\s?''?-?([\w\d().]*?)''?,';
This looks behind for thingX' and then tries to match : followed by zero or one spaces, followed by 0 or 1 single quote, followed by zero or one dash, followed by any combination of letters, numbers, parentheses, or periods (this is defined as the token), using a lazy match, until zero or one single quote is encountered, followed by a comma. I call regexp as regexp(___,'tokens','once') to return the matching token.
The problem is that when there is no match, regexp returns an empty array. This prevents me from using, say,
out=cellfun(#(x) regexp(x,expr3,'tokens','once'),mycell);
unless I call it with 'UniformOutput',false. The problem with that is twofold. First, I need to then manually find the rows where there was no match. For example, I can do this:
emptyout=cellfun(#(x) isempty(x),out);
emptyID=find(emptyout);
backfill=cell(length(emptyID),1);
[backfill{:}]=deal('Unknown');
out(emptyID)=backfill;
In this example, emptyID has a length of 1 so this code is overkill. But I believe this is the correct way to generalize for when it is longer. This code will change every empty cell array in out with the string Unknown. But this leads to the second problem. I've now got a 'messy' cell array of non-scalar values. I cannot, for example, check unique(out) as a result.
Pardon the long-windedness but I wanted to give a clear example of the problem. Now my actual question is in a few parts:
Is there a way to accomplish what I'm trying to do without using 'UniformOutput',false? For example, is there a way to have regexp pass a custom string if there is no match (e.g. pass 'Unknown' if there is no match)? I can think of one 'cheat', which would be to use the | operator in the expression, and if the first token is not matched, look for something that is ALWAYS found. I would then still need to double back through the output and change every instance of that result to 'Unknown'.
If I take the 'UniformOutput',false approach, how can I recover a scalar cell array at the end to easily manipulate it (e.g. pass it through unique)? I will admit I'm not 100% clear on scalar vs nonscalar cell arrays.
If there is some overall different approach that I'm not thinking of, I'm also open to it.
Tangential to the main question, I also tried using a single expression to run regexp using 3 tokens to pull out the values of thing1, thing2, and thing3 in one pass. This seems to require 'UniformOutput',false even when there are no empty results from regexp. I'm not sure how to get a scalar cell array using this approach (e.g. an Nx1 cell array where each cell is a 3x1 cell).
At the end of the day, I want to build a table using these results:
mytable=table(out1,out2,out3);
Edit: Using celldisp sheds some light on the problem:
celldisp(out)
out{1}{1} =
246
out{2} =
Unknown
out{3}{1} =
246
I assume that I need to change the structure of out so that the contents of out{1}{1} and out{3}{1} are instead just out{1} and out{3}. But I'm not sure how to accomplish this if I need 'UniformOutput',false.
Note: I've not used MATLAB and this doesn't answer the "efficient" aspect, but...
How about forcing there to always be a match?
Just thinking about you really wanting a match to skip this problem, how about an empty match?
Looking on the MATLAB help page here I can see a 'emptymatch' option, perhaps this is something to try.
E.g.
the_thing_i_want_to_find|
Match "the_thing_i_want_to_find" or an empty match, note the | character.
In capture group it might look like this:
(the_thing_i_want_to_find|)
As a workaround, I have found that using regexprep can be used to find entries where thing3 is missing. For example:
replace='$1 ''thing3'': ''Unknown'', ''morestuff''';
missingexpr='(?<=thing2'':\s?)(''?-?[\w\d().]*?''?,) ''morestuff''';
regexprep(mycell{2},missingexpr,replace)
ans =
''thing1': '617', 'thing2': '239', 'thing3': 'Unknown', 'morestuff':, '''
Applying it to the entire array:
fixedcell=cellfun(#(x) regexprep(x,missingexpr,replace),mycell);
out=cellfun(#(x) regexp(x,expr3,'tokens','once'),fixedcell,'UniformOutput',false);
This feels a little roundabout, but it works.
cellfun can be replaced with a plain old for loop. Your code will either be equally fast, or maybe even faster. cellfun is implemented with a loop anyway, there is no advantage of using it other than fewer lines of code. In your explicit loop, you can then check the output of regexp, and build your output array any way you like.
My question is a continuation of this one. Basically, I have a table of words like so:
HAT18178_890909.098070313.1
HAT18178_890909.098070313.2
HAT18178_890909.143412462.1
HAT18178_890909.143412462.2
For my purposes, I do not need the terminal .1 or .2 for this set of names. I can manually write the following regex (using Python syntax):
r = re.compile('(.*\.\d+)\.\d+')
However, I cannot guarantee that my next set of names will have a similar structure where the final 2 characters will be discardable - it could be 3 characters (i.e. .12) and the separator could change as well (i.e. . to _).
What is the appropriate way to either explicitly learn a regex or to determine which characters are unnecessary?
It's an interesting problem.
X y
HAT18178_890909.098070313.1 HAT18178_890909.098070313
HAT18178_890909.098070313.2 HAT18178_890909.098070313
HAT18178_890909.143412462.1 HAT18178_890909.143412462
HAT18178_890909.143412462.2 HAT18178_890909.143412462
The problem is that there is not a single solution but many.
Even for a human it is not clear what the regex should be that you want.
Based on this data, I would think the possibilities to learn are:
Just match a fixed width of 25: .{25}
Fixed first part: HAT18178_890909.
Then:
There's only 2 varying numbers on each single spot (as you show 2 cases).
So e.g. [01] (either 0 or 1), [94] the next spot and so on would be a good solution.
The obvious one would be \d+
But it could also be \d{9}
You see, there are multiple correct answers.
These regexes would still work if the second point would be an underscore instead.
My conclusion:
The problem is that it is much more work to prepare the data for machine learning than it is to create a regex. If you want to be sure you cover everything, you need to have complete data, so then a regex is probably less effort.
You could split on non-alphanumeric characters;
[^a-zA-Z0-9']+
That would get you, in this case, few strings like this:
HAT18178
890909
098070313
1
From there on you can simply discard the last one if that's never necessary, and continue on processing the first sequences
Fairly new to classic ASP(maintaining legacy applications) and I need to figure out how to fish out values from a string. String itself can look something like this - 0,12,234,543. I was thinking about making a function where I can specify which number I want from the string for ex.
Function fnGetNumber(string, 3)
// returns the third number(number after the second comma ie. 234)
End Function
The string will always have only numbers and always 4 of them. Also they will not have decimal places.
The function itself is not a problem, but I can't figure out the regex.
Using Split is the way, use it to transform the string to an array and pull the data from that.
I wouldn't recommend regex as whilst it powerful, its readability is poor.
I have a text file which I geline to a string. The file is like this: 0.2abc 0.2 .2abc .2 abc.2abc abc.2 abc0.20 .2 . 20
I wanna check the result then parse it in to separate float. The result is:0.2 0.2abc 2 20 2abc abc0.20 abc
This is expalined: check if there is 2 digit (before and after '.' (full stop)) whether with char or not. If only 1 site of the '.' is digit the '.' will be full stop.
How can I parse a STRING to separate result like that? I did use iterator to check the '.' and pos of it, but still got stuck.
The first thing you need to do is split the input in words. Easy, just don't use .getline()
but instead rely on `while (cin >> strWord ) { /* do stuff with word*/ };
The second thing is to kick out bad input words early: words of 2 characters or less, with more than one ., or with the . first or last.
You now know that the . is somewhere in the middle. find() will give you an iterator. ++ and -- give you the next and previous iterators. * gives you the character that the iterator points to. isdigit() tells you whether that character is a digit. Add ingredients together and you're done.
Seems like some fairly complicated advice above -- and not necessarily helpful.
Your question does not make it entirely clear what the end result should look like. Do you want an array of floating point numbers? Do you just want the sum? Do you want to print out the results?
If you want help with homework, the best policy is to post your own attempt and then others can help you improve it, to make it work.
One approach that might help is to try to break the string into sub-strings (tokens) and discard the junk.
Write a function that accepts a character and returns true (this is part of a floating point number) or false (it isn't).
Scan along the string using an iterator or an index.
While current char is not part of a token, skip it.
If you find a token char, while current char is part of a token, copy it to another string
etc. to get all floating point substrings.
Then you can use std::stringstream or ::atof() to convert.
Have a bit of a go and post what you can get done.
sounds like you could use some regex to extract your number.
Try this regex in order to extract the floating values within a string.
[0-9]+\.[0-9]+
Keep in mind that this won't extract integer values. ie 234abc
I don't know if there is a built-in way to use regex in c++ but i found this library with a quick google search which allows you to use regex in c++
Sounds like you should look at the "Interpreter" Design Pattern.
Or you could use the "State" Design Pattern and do it by hand.
There should be plenty of examples of both on the web.