CODEWITHSUNDEEP
pythonregex
user196264097
user196264097

Reputation: 887

How can i search and replace using python regex

I want to make the function which find for string in the array and then replace the corres[ponding element from the dictionary. so far i have tried this but i am not able to figure out few things like

  1. How can escape special characters
  2. I can i replace with match found. i tried \1 but it didn't work

dsds

def myfunc(h):
        myarray = {
                "#":"\\#",
                "$":"\\$",
                "%":"\\%",
                "&":"\\&",
                "~":"\\~{}",
                "_":"\\_",
                "^":"\\^{}",
                "\\":"\\textbackslash{}",
                "{":"\\{",
                "}":"\\}"                
                    }
        pattern = "[#\$\%\&\~\_\^\\\\\{\}]"
        pattern_obj = re.compile(pattern, re.MULTILINE)
        new = re.sub(pattern_obj,myarray[\1],h)

        return new

Upvotes: 0

Views: 108

Answers (4)

Aleksei Zyrianov
Aleksei Zyrianov

Reputation: 2342

  1. I'd suggest you to use raw literal syntax (r"") for better readability of the code.
  2. For the case of your array you may want just to use str.replace function instead of re.sub.
def myfunc(h):
    myarray = [
            ("\\", r"\textbackslash"),
            ("{", r"\{"),
            ("}", r"\}"),
            ("#", r"\#"),
            ("$", r"\$"),
            ("%", r"\%"),
            ("&", r"\&"),
            ("~", r"\~{}"),
            ("_", r"\_"),
            ("^", r"\^{}")]

    for (val, replacement) in myarray:
        h = h.replace(val, replacement)
    h = h.replace(r"\textbackslash", r"\textbackslash{}", h)

    return h

The code is a modification of @tigger's answer.

Upvotes: 1

georg
georg

Reputation: 215039

You're looking for re.sub callbacks:

def myfunc(h):
    rules = {
            "#":r"\#",
            "$":r"\$",
            "%":r"\%",
            "&":r"\&",
            "~":r"\~{}",
            "_":r"\_",
            "^":r"\^{}",
            "\\":r"\textbackslash{}",
            "{":r"\{",
            "}":r"\}"                
    }
    pattern = '[%s]' % re.escape(''.join(rules.keys()))
    new = re.sub(pattern, lambda m: rules[m.group()], h)
    return new

This way you avoid 1) loops, 2) replacing already processed content.

Upvotes: 3

Anil Vaitla
Anil Vaitla

Reputation: 2978

You can try to use re.sub inside a loop that iterates over myarray.items(). However, you'll have to do backslash first since otherwise that might replace things incorrectly. You also need to make sure that "{" and "}" happen first, so that you don't mix up the matching. Since dictionaries are unordered I suggest you use list of tuples instead:

def myfunc(h):
    myarray = [
            ("\\","\\textbackslash")
            ("{","\\{"),
            ("}","\\}"),
            ("#","\\#"),
            ("$","\\$"),
            ("%","\\%"),
            ("&","\\&"),
            ("~","\\~{}"),
            ("_","\\_"),
            ("^","\\^{}")]

    for (val, replacement) in myarray:
        h = re.sub(val, replacement, h)
    h = re.sub("\\textbackslash", "\\textbackslash{}", h)

    return h

Upvotes: 1

Elazar
Elazar

Reputation: 21685

to escape metacharacters, use raw string and backslashes

r"regexp with a \* in it"

Upvotes: 0

Related Questions