Replace Multiple Characters in One Replace Call

Replace multiple characters in one replace call

If you want to replace multiple characters you can call the String.prototype.replace() with the replacement argument being a function that gets called for each match. All you need is an object representing the character mapping that you will use in that function.

For example, if you want a replaced with x, b with y, and c with z, you can do something like this:

const chars = {'a':'x','b':'y','c':'z'};
let s = '234abc567bbbbac';
s = s.replace(/[abc]/g, m => chars[m]);
console.log(s);

Output: 234xyz567yyyyxz

How can I replace multiple characters in a string?

Doesn't seem this even needs regex. Just 2 chained replacements would do.

var str = '[T] and [Z] but not [T] and [Z]';var result = str.replace('T',' ').replace('Z','');console.log(result);

Replace multiple strings with multiple other strings

As an answer to:

looking for an up-to-date answer

If you are using "words" as in your current example, you might extend the answer of Ben McCormick using a non capture group and add word boundaries \b at the left and at the right to prevent partial matches.

\b(?:cathy|cat|catch)\b

\b A word boundary to prevent a partial match
(?: Non capture group
- cathy|cat|catch match one of the alternatives
) Close non capture group
\b A word boundary to prevent a partial match

Example for the original question:

let str = "I have a cat, a dog, and a goat.";
const mapObj = {
  cat: "dog",
  dog: "goat",
  goat: "cat"
};
str = str.replace(/\b(?:cat|dog|goat)\b/gi, matched => mapObj[matched]);
console.log(str);

How to replace multiple substrings of a string?

Here is a short example that should do the trick with regular expressions:

import re

rep = {"condition1": "", "condition2": "text"} # define desired replacements here

# use these three lines to do the replacement
rep = dict((re.escape(k), v) for k, v in rep.iteritems()) 
#Python 3 renamed dict.iteritems to dict.items so use rep.items() for latest versions
pattern = re.compile("|".join(rep.keys()))
text = pattern.sub(lambda m: rep[re.escape(m.group(0))], text)

For example:

>>> pattern.sub(lambda m: rep[re.escape(m.group(0))], "(condition1) and --condition2--")
'() and --text--'

Best way to replace multiple characters in a string?

Replacing two characters

I timed all the methods in the current answers along with one extra.

With an input string of abc&def#ghi and replacing & -> \& and # -> \#, the fastest way was to chain together the replacements like this: text.replace('&', '\&').replace('#', '\#').

Timings for each function:

a) 1000000 loops, best of 3: 1.47 μs per loop
b) 1000000 loops, best of 3: 1.51 μs per loop
c) 100000 loops, best of 3: 12.3 μs per loop
d) 100000 loops, best of 3: 12 μs per loop
e) 100000 loops, best of 3: 3.27 μs per loop
f) 1000000 loops, best of 3: 0.817 μs per loop
g) 100000 loops, best of 3: 3.64 μs per loop
h) 1000000 loops, best of 3: 0.927 μs per loop
i) 1000000 loops, best of 3: 0.814 μs per loop

Here are the functions:

def a(text):
    chars = "&#"
    for c in chars:
        text = text.replace(c, "\\" + c)

def b(text):
    for ch in ['&','#']:
        if ch in text:
            text = text.replace(ch,"\\"+ch)

import re
def c(text):
    rx = re.compile('([&#])')
    text = rx.sub(r'\\\1', text)

RX = re.compile('([&#])')
def d(text):
    text = RX.sub(r'\\\1', text)

def mk_esc(esc_chars):
    return lambda s: ''.join(['\\' + c if c in esc_chars else c for c in s])
esc = mk_esc('&#')
def e(text):
    esc(text)

def f(text):
    text = text.replace('&', '\&').replace('#', '\#')

def g(text):
    replacements = {"&": "\&", "#": "\#"}
    text = "".join([replacements.get(c, c) for c in text])

def h(text):
    text = text.replace('&', r'\&')
    text = text.replace('#', r'\#')

def i(text):
    text = text.replace('&', r'\&').replace('#', r'\#')

Timed like this:

python -mtimeit -s"import time_functions" "time_functions.a('abc&def#ghi')"
python -mtimeit -s"import time_functions" "time_functions.b('abc&def#ghi')"
python -mtimeit -s"import time_functions" "time_functions.c('abc&def#ghi')"
python -mtimeit -s"import time_functions" "time_functions.d('abc&def#ghi')"
python -mtimeit -s"import time_functions" "time_functions.e('abc&def#ghi')"
python -mtimeit -s"import time_functions" "time_functions.f('abc&def#ghi')"
python -mtimeit -s"import time_functions" "time_functions.g('abc&def#ghi')"
python -mtimeit -s"import time_functions" "time_functions.h('abc&def#ghi')"
python -mtimeit -s"import time_functions" "time_functions.i('abc&def#ghi')"

Replacing 17 characters

Here's similar code to do the same but with more characters to escape (\`*_{}>#+-.!$):

def a(text):
    chars = "\\`*_{}[]()>#+-.!$"
    for c in chars:
        text = text.replace(c, "\\" + c)

def b(text):
    for ch in ['\\','`','*','_','{','}','[',']','(',')','>','#','+','-','.','!','$','\'']:
        if ch in text:
            text = text.replace(ch,"\\"+ch)

import re
def c(text):
    rx = re.compile('([&#])')
    text = rx.sub(r'\\\1', text)

RX = re.compile('([\\`*_{}[]()>#+-.!$])')
def d(text):
    text = RX.sub(r'\\\1', text)

def mk_esc(esc_chars):
    return lambda s: ''.join(['\\' + c if c in esc_chars else c for c in s])
esc = mk_esc('\\`*_{}[]()>#+-.!$')
def e(text):
    esc(text)

def f(text):
    text = text.replace('\\', '\\\\').replace('`', '\`').replace('*', '\*').replace('_', '\_').replace('{', '\{').replace('}', '\}').replace('[', '\[').replace(']', '\]').replace('(', '\(').replace(')', '\)').replace('>', '\>').replace('#', '\#').replace('+', '\+').replace('-', '\-').replace('.', '\.').replace('!', '\!').replace('$', '\$')

def g(text):
    replacements = {
        "\\": "\\\\",
        "`": "\`",
        "*": "\*",
        "_": "\_",
        "{": "\{",
        "}": "\}",
        "[": "\[",
        "]": "\]",
        "(": "\(",
        ")": "\)",
        ">": "\>",
        "#": "\#",
        "+": "\+",
        "-": "\-",
        ".": "\.",
        "!": "\!",
        "$": "\$",
    }
    text = "".join([replacements.get(c, c) for c in text])

def h(text):
    text = text.replace('\\', r'\\')
    text = text.replace('`', r'\`')
    text = text.replace('*', r'\*')
    text = text.replace('_', r'\_')
    text = text.replace('{', r'\{')
    text = text.replace('}', r'\}')
    text = text.replace('[', r'\[')
    text = text.replace(']', r'\]')
    text = text.replace('(', r'\(')
    text = text.replace(')', r'\)')
    text = text.replace('>', r'\>')
    text = text.replace('#', r'\#')
    text = text.replace('+', r'\+')
    text = text.replace('-', r'\-')
    text = text.replace('.', r'\.')
    text = text.replace('!', r'\!')
    text = text.replace('$', r'\$')

def i(text):
    text = text.replace('\\', r'\\').replace('`', r'\`').replace('*', r'\*').replace('_', r'\_').replace('{', r'\{').replace('}', r'\}').replace('[', r'\[').replace(']', r'\]').replace('(', r'\(').replace(')', r'\)').replace('>', r'\>').replace('#', r'\#').replace('+', r'\+').replace('-', r'\-').replace('.', r'\.').replace('!', r'\!').replace('$', r'\$')

Here's the results for the same input string abc&def#ghi:

a) 100000 loops, best of 3: 6.72 μs per loop
b) 100000 loops, best of 3: 2.64 μs per loop
c) 100000 loops, best of 3: 11.9 μs per loop
d) 100000 loops, best of 3: 4.92 μs per loop
e) 100000 loops, best of 3: 2.96 μs per loop
f) 100000 loops, best of 3: 4.29 μs per loop
g) 100000 loops, best of 3: 4.68 μs per loop
h) 100000 loops, best of 3: 4.73 μs per loop
i) 100000 loops, best of 3: 4.24 μs per loop

And with a longer input string (## *Something* and [another] thing in a longer sentence with {more} things to replace$):

a) 100000 loops, best of 3: 7.59 μs per loop
b) 100000 loops, best of 3: 6.54 μs per loop
c) 100000 loops, best of 3: 16.9 μs per loop
d) 100000 loops, best of 3: 7.29 μs per loop
e) 100000 loops, best of 3: 12.2 μs per loop
f) 100000 loops, best of 3: 5.38 μs per loop
g) 10000 loops, best of 3: 21.7 μs per loop
h) 100000 loops, best of 3: 5.7 μs per loop
i) 100000 loops, best of 3: 5.13 μs per loop

Adding a couple of variants:

def ab(text):
    for ch in ['\\','`','*','_','{','}','[',']','(',')','>','#','+','-','.','!','$','\'']:
        text = text.replace(ch,"\\"+ch)

def ba(text):
    chars = "\\`*_{}[]()>#+-.!$"
    for c in chars:
        if c in text:
            text = text.replace(c, "\\" + c)

With the shorter input:

ab) 100000 loops, best of 3: 7.05 μs per loop
ba) 100000 loops, best of 3: 2.4 μs per loop

With the longer input:

ab) 100000 loops, best of 3: 7.71 μs per loop
ba) 100000 loops, best of 3: 6.08 μs per loop

So I'm going to use ba for readability and speed.

Addendum

Prompted by haccks in the comments, one difference between ab and ba is the if c in text: check. Let's test them against two more variants:

def ab_with_check(text):
    for ch in ['\\','`','*','_','{','}','[',']','(',')','>','#','+','-','.','!','$','\'']:
        if ch in text:
            text = text.replace(ch,"\\"+ch)

def ba_without_check(text):
    chars = "\\`*_{}[]()>#+-.!$"
    for c in chars:
        text = text.replace(c, "\\" + c)

Times in μs per loop on Python 2.7.14 and 3.6.3, and on a different machine from the earlier set, so cannot be compared directly.

╭────────────╥──────┬───────────────┬──────┬──────────────────╮
│ Py, input  ║  ab  │ ab_with_check │  ba  │ ba_without_check │
╞════════════╬══════╪═══════════════╪══════╪══════════════════╡
│ Py2, short ║ 8.81 │    4.22       │ 3.45 │    8.01          │
│ Py3, short ║ 5.54 │    1.34       │ 1.46 │    5.34          │
├────────────╫──────┼───────────────┼──────┼──────────────────┤
│ Py2, long  ║ 9.3  │    7.15       │ 6.85 │    8.55          │
│ Py3, long  ║ 7.43 │    4.38       │ 4.41 │    7.02          │
└────────────╨──────┴───────────────┴──────┴──────────────────┘

We can conclude that:

Those with the check are up to 4x faster than those without the check
ab_with_check is slightly in the lead on Python 3, but ba (with check) has a greater lead on Python 2
However, the biggest lesson here is Python 3 is up to 3x faster than Python 2! There's not a huge difference between the slowest on Python 3 and fastest on Python 2!

Replace multiple characters in one line Javascript

Try regular expression

dragdropMatchResponseData.replace(/\[,\]/g, ':').replace(/\[:\]/g, ',')

The /g flag is to replace all the occurances within the string.

Replace multiple characters in a string at once

You are using a literal 'replacing_words' instead of the variable i inside your for-loop.
You don't replace the original string to modify it again, instead you create a new string, resulting in only the last replacement to be shown

Here would be the correct code.

string = input('Enter something to change')
vowels = 'aeiouy'

for i in vowels:
    string = string.replace(i, ' ')

print(string)

Also, I think input returns a string 'type'. So calling str will have no effect. Not sure. Also #2: y is a vowel as well (so are åäö and other umlauts and weird characters if you want to be thorough).

Replace multiple character with a single character

An option with str_replace

library(stringr)
str_replace(string, "[.]+", " - ")
#[1] "oxalic - R"     "gentamicin - C" "penicilin - R"

Replace Multiple Characters in One Replace Call