RegEx for adding a char in specific places

Question

I am trying to analyze Javadoc comments in python and for that, I need full stops for splitting. How can I add full stops in the right places in a Javadoc comment?

I want something like this: Input:

/**
     * The addVertex method checks to see if the vertex isn't null, and then if
     * the graph does not contain the vertex, the vertex is then added and true
     * is returned
     *
     * @param vertex
     *
     * @throws NullPointerException.
     *
     * @return b
     */

Output:

/**
     * The addVertex method checks to see if the vertex isn't null, and then if
     * the graph does not contain the vertex, the vertex is then added and true
     * is returned.*here*
     *
     * @param vertex.*here*
     *
     * @throws NullPointerException.*here*
     *
     * @return b.*here*
     */

Note: If a full stop/semicolon/comma already exists, then replacement is not required since my program splits on the basis of these 3 punctuation marks.

In addition, Javadoc descriptions can have inline tags, like {@link...}, no punctuation marks are required around this.

Only before @param, @throw, @return(at the end as well) is required.

SOLUTION

test_str = ("/**\n"
    "     * The addVertex method checks to see if the vertex isn't null, and then if\n"
    "     * the graph does not contain the vertex, the vertex is then added and true\n"
    "     * is returned\n"
    "     *\n"
    "     * @param vertex\n"
    "     *\n"
    "     * @throws NullPointerException.\n"
    "     *\n"
    "     * @return b\n"
    "     */")

result = re.sub(r'(@param|@throw|@return)', r'.\1', test_str)
print(result)

This adds a full stop in the places required except for after the last tag, not a problem for splitting!

Answer 1

For those with missing ., you can simply write an expression maybe similar to:

(\* @param|@return)(.*)

which you can replace it with $1$2.

RegEx

You can modify/change your expressions in regex101.com.

RegEx Circuit

You can also visualize your expressions in jex.im:

JavaScript Demo

const regex = /(\* @param|@return)(.*)/gm;
const str = `/**
     * The addVertex method checks to see if the vertex isn't null, and then if
     * the graph does not contain the vertex, the vertex is then added and true
     * is returned
     *
     * @param vertex
     *
     * @throws NullPointerException.
     *
     * @return b
     */`;
const subst = `$1$2.`;

// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);

console.log('Substitution result: ', result);

Python Code:

# coding=utf8
# the above tag defines encoding for this document and is for Python 2.x compatibility

import re

regex = r"(\* @param|@return)(.*)"

test_str = ("/**\n"
    "     * The addVertex method checks to see if the vertex isn't null, and then if\n"
    "     * the graph does not contain the vertex, the vertex is then added and true\n"
    "     * is returned\n"
    "     *\n"
    "     * @param vertex\n"
    "     *\n"
    "     * @throws NullPointerException.\n"
    "     *\n"
    "     * @return b\n"
    "     */")

subst = "\\1\\2."

# You can manually specify the number of replacements by changing the 4th argument
result = re.sub(regex, subst, test_str, 0, re.MULTILINE)

if result:
    print (result)

# Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.

Output

/**
     * The addVertex method checks to see if the vertex isn't null, and then if
     * the graph does not contain the vertex, the vertex is then added and true
     * is returned
     *
     * @param vertex.
     *
     * @throws NullPointerException.
     *
     * @return b.
     */

Expression for description

If you like to add a . after description, this expression might work:

([\s\*]+@param)

Python Code

# coding=utf8
# the above tag defines encoding for this document and is for Python 2.x compatibility

import re

regex = r"([\s\*]+@param)"

test_str = ("/**\n"
    "     * The addVertex method checks to see if the vertex isn't null, and then if\n"
    "     * the graph does not contain the vertex, the vertex is then added and true\n"
    "     * is returned\n"
    "     *\n"
    "     * @param vertex\n"
    "     *\n"
    "     * @throws NullPointerException.\n"
    "     *\n"
    "     * @return b\n"
    "     */")

subst = ".\\1"

# You can manually specify the number of replacements by changing the 4th argument
result = re.sub(regex, subst, test_str, 0, re.MULTILINE)

if result:
    print (result)

# Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.