Regex replace python4/30/2023 ![]() ![]() I assume it's 4 backslashes but I honestly expected only 2 would have been needed due to the raw string r construct. I'm also curious how to match literal backslashes now in the regex. If anyone can comment on that it would be appreciated. ![]() The double backslashes I believe are there so that the regex receives a literal backslash.ītw, I am surprised it printed double backslashes instead of a single one. _ppt='(let H : forall x : bool, negb (negb x) = x := fun x : bool =>HEREinHERE)' Out: '(let H : forall x : bool, negb (negb x) = x := fun x : bool =>HEREinHERE)' parenthesis ( are not interpreted as was to group this but literally code I have in my app: # escapes non-alphanumeric to help match arbitrary literal string, I think the reason this is here is to help differentiate the things escaped from the regex we are inserting in the next line and the literal things we wanted escaped. It is a built-in Python method in re module that returns replaced string. things that would be usually ignored by the regex paraser e.g. To replace a string in Python, the regex sub() method is used. Thus we usually do re.escape(regex) to escape things we want to be interpreted literally i.e. For that you need r"(\fun \( x : nat \) :)" here the first parens won't be matched since it's a capture group due to lack of backslashes but the second one will be matched as literal parens. However, the regex will receive a parenthesis and won't match it as a literal parenthesis unless you tell it to explicitly using the regex's own syntax rules. I believe this is why we are recommended to pass raw strings like r"(\n ) - so that the regex receives what you actually typed. The regex parser will interpret the strings it's receives differently than python's print would. To complicate things further there is another syntax/grammar going on with regexes. Syntax: re. There are in total 5 arguments of this function. It is used for substituting a specific pattern in the string. If you do \r"\n" then python will always interpret it as the raw thing you typed in (as far as I understand). The re.sub () method performs global search and global replace on the given string. Once you pass it through python's print will display it and thus parse it as a new a line but in the text you see in the editor it's likely just the char for backslash followed by n. When you see in your editor \n it's not really a new line until the parser decides it is. Besides a regular expression, the pattern can be Pattern object. ![]() The sub () function has the following syntax: re.sub (pattern, repl, string, count 0, flags 0) Code language: Python (python) In this syntax: pattern is a regular expression that you want to match. Remember usually you type strings into your compuer and the computer insert the specific characters. The sub () is a function in the built-in re module that handles regular expressions. Usually escaping the string that you feed into a regex is such that the regex considers those characters literally. ![]()
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