Replace Method Doesn't Work

Why does String.replace not work?

You did not assign it to test. Strings are immutable.

test = test.replace("KP", "");

You need to assign it back to test.

Why isn't the replace() function working?

strings are immutable. so header_raw_text.replace() does not change the string itself.you have to do reassign the result after replacing.

header_raw_text = header_raw_text.replace("arrow_upward ", "")

Why replace() doesn't work in my Python function?

replace is not a in-place method, but instead it returns a new string, so you need to assign the result to a new string.

From the docs: https://docs.python.org/3/library/stdtypes.html#str.replace

str.replace(old, new[, count])

Return a copy of the string with all occurrences of substring old replaced by new. If the optional argument count is given, only the first count occurrences are replaced.

Also your logic can be simplified a lot like below, if you iterate on key and value together

def replace_exception_chars(string):
    exception_chars_dict = {'Old': 'New', 'old': 'new'}

    #Iterate over key and value together
    for key, value in exception_chars_dict.items():
        #If key is found, replace key with value and assign to new string
        if key in string:
            string = string.replace(key, value)

    return string

print(replace_exception_chars('Old, not old'))

The output will be

New, not new

replace() method not working on Pandas DataFrame

You need to assign back

df = df.replace('white', np.nan)

or pass param inplace=True:

In [50]:
d = {'color' : pd.Series(['white', 'blue', 'orange']),
   'second_color': pd.Series(['white', 'black', 'blue']),
   'value' : pd.Series([1., 2., 3.])}
df = pd.DataFrame(d)
df.replace('white', np.nan, inplace=True)
df

Out[50]:
    color second_color  value
0     NaN          NaN    1.0
1    blue        black    2.0
2  orange         blue    3.0

Most pandas ops return a copy and most have param inplace which is usually defaulted to False

replace() function not working as intended

String.prototype.replace()

The replace() method returns a new string with some or all matches of a pattern replaced by a replacement.

You have to reassign the new value to the variable (word).

const getLetterCount = (stringToTest) => {
  const wordArray = stringToTest.split('');
  let totalLetters = 0;
  for (let word of wordArray) {
    word = word.replace(/[.,\/#!$%\^&\*;:{}=\-_` ~()]/g, "");
    totalLetters += word.length;
  }
 console.log(totalLetters);
}

getLetterCount('boy/girl?')  // returns 9 ( counting punctuation as well)

Why my contains and replace method doesn't work right?

Change the replace method call to:

str1 = str1.replace("replace", "Hi");

Since String are immutable, you need to reassign the result back to str1. It doesn't perform in-place replacement, rather it constructs and returns a new String object. the original String is unmodified.

Python String replace doesn't work

Strings are immutable. That means that they cannot be changed. stringT.replace(...) does not change stringT itself; it returns a new string. Change that line to:

stringT = stringT.replace("world", "all")

JavaScript replace doesn't work

barea = barea.replace(area, "cu")

You need to assign it since String.prototype.replace isn't a mutator method.

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