Regex to Remove Certain Characters At the Beginning and End of a String

Regular Expression to Remove Beginning and End chars from a string?

$file = preg_replace('/^widget-|\.php$/', '', $file);

Remove specific character if at the beginning of a string or consecutive at any place in a string

You might use an alternation and a character class listing all the characters that you want to remove at the start of the string, the end or repeated 2 or more times using {2,}

^[ *'0-9?&_$-]+|[ *'0-9?&_$-]+$|[ *'0-9?&_$-]{2,}

Regex demo

If you want to remove all except characters a-zA-Z and a negated character class to match any character not in the character class

In the replacement use an empty string.

^[^a-zA-Z]+|[^a-zA-Z]+$|[^a-zA-Z]{2,}

Regex demo

regex to remove certain characters at the beginning and end of a string

First match the dots, capture and lazy-repeat any character until you get to .bye, and match the .bye. Then, you can replace with the first captured group, plus an exclamation mark:

const str = '...hello world.bye';console.log(str.replace(/\.\.\.(.*)\.bye/, '$1!'));

Regex Expression to remove certain characters from string expect at the start and end

Probably something like this should work:

(?!^\%*)[^\w\s](?<!\%$)

Your error stands in the fact that the sequence ^\%^ will never occur since you are asking that the start of the sequence is after a % sign. Also the universal quantifier belongs to the % sign and not to the negative group. You should also check for the end of the line $. The rest was fine

regex for removing characters at end of string

[ ,;:/]*$ should be what you need. This is the same as your current regex except with the $ on the end. The $ tells it that the match must happen at the end of the string.

How to remove anything that starts with specific character (@) in various locations in string in R?

We may change the pattern to match zero or more space (\\s*) followed by @ and one or more non-white space (\\S+) in str_remove_all to remove those substring

library(stringr)
library(dplyr)
Customer %>%
mutate(Cleaned_Tweet = str_remove_all(Tweet, "\\s*@\\S+"))

-output

 ID                                                                 Tweet                                         Cleaned_Tweet
1 1 @ChipotleTweets @ChipotleTweets Becky is very nice Becky is very nice
2 2 Happy Halloween! I now look forward to $3 booritos at @ChipotleTweets Happy Halloween! I now look forward to $3 booritos at
3 3 Considering walking to @.ChipotleTweets in my llama onesie. Considering walking to in my llama onesie.

NOTE: str_remove just removes the first instance of match i.e. if there are more than one match in a single string, it skips the others and matches only the first. We need str_remove_all for removing all instances of matching patterns.

data

Customer <- structure(list(ID = 1:3, Tweet = c("@ChipotleTweets @ChipotleTweets Becky is very nice", 
"Happy Halloween! I now look forward to $3 booritos at @ChipotleTweets",
"Considering walking to @.ChipotleTweets in my llama onesie."
)), class = "data.frame", row.names = c(NA, -3L))

How to remove special characters from the beginning of a string in Python

You could use a regular expression:

import re
mystring = re.sub(r"^\W+", "", mystring)

This removes all non-alphanumeric characters from the start of your string:

Explanation:

^   # Start of string
\W+ # One or more non-alphanumeric characters

Regular expression to remove special characters from start or end of a string

Can be simplified like this:

  res = re.sub(r'^\W+|\W+$', '', txt)


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