Changing one character in a string

Question

What is the easiest way in Python to replace a character in a string   For example   text    abcdefg   text 1     Z

User · Answer

A solution combining find and replace methods in a single line if statement could be     python my var    quot stackoverflaw quot  my new var   my var replace  a    o   1  if my var find  s      -1 else my var print f quot my var    my var  quot               my var   stackoverflaw print f quot my new var    my new var  quot       my new var   stackoverflow

User · Answer

I would like to add another way of changing a character in a string    gt  gt  gt  text                  gt  gt  gt  text   text  1     text 1   replace text 0        1                   How faster it is when compared to turning the string into list and replacing the ith value then joining again    List approach   gt  gt  gt  timeit timeit  text                  s   list text   s 1            join s    number 1000000  0 8268570480013295   My solution   gt  gt  gt  timeit timeit  text                  text text  1     text 1   replace text 0        1     number 1000000  0 588400217000526

User · Answer

Don t modify strings   Work with them as lists  turn them into strings only when needed    gt  gt  gt  s   list  Hello zorld    gt  gt  gt  s   H    e    l    l    o         z    o    r    l    d    gt  gt  gt  s 6     W   gt  gt  gt  s   H    e    l    l    o         W    o    r    l    d    gt  gt  gt     join s   Hello World    Python strings are immutable  i e  they can t be modified    There are a lot of reasons for this   Use lists until you have no choice  only then turn them into strings

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Starting with python 2 6 and python 3 you can use bytearrays which are mutable  can be changed element-wise unlike strings    s    abcdefg  b s   bytearray s  b s 1     Z  s   str b s  print s aZcdefg   edit  Changed str to s  edit2  As Two-Bit Alchemist mentioned in the comments  this code does not work with unicode

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new   text  1     Z    text 2

User · Answer

Fastest method   There are three ways  For the speed seekers I recommend  Method 2    Method 1  Given by this answer  text    abcdefg  new   list text  new 6     W     join new    Which is pretty slow compared to  Method 2   timeit timeit  text    abcdefg   s   list text   s 6     W      join s    number 1000000  1 0411581993103027   Method 2  FAST METHOD   Given by this answer  text    abcdefg  text   text  1     Z    text 2     Which is much faster   timeit timeit  text    abcdefg   text   text  1     Z    text 2     number 1000000  0 34651994705200195   Method 3   Byte array   timeit timeit  text    abcdefg   s   bytearray text   s 1     Z   str s    number 1000000  1 0387420654296875

User · Answer

Like other people have said  generally Python strings are supposed to be immutable   However  if you are using CPython  the implementation at python org  it is possible to use ctypes to modify the string structure in memory   Here is an example where I use the technique to clear a string   Mark data as sensitive in python  I mention this for the sake of completeness  and this should be your last resort as it is hackish

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if your world is 100  ascii utf-8 a lot of use cases fit in that box    b   bytearray s   utf-8     process - e g   lowercasing        b 0    b i 1  - 32 s   str b   utf-8     python 3 7 3

User · Answer

Strings are immutable in Python  which means you cannot change the existing string  But if you want to change any character in it  you could create a new string out it as follows  def replace s  position  character       return s  position    character   s position 1    replace  King   1   o       result  Kong Note  If you give the position value greater than the length of the string  it will append the character at the end  replace  Dog   10   s       result  Dogs

User · Answer

This code is not mine  I couldn t recall the site form where  I took it  Interestingly  you can use this to replace one character or more with one or more charectors  Though this reply is very late  novices like me  anytime  might find it useful  Change Text function  mytext    Hello Zorld  mytext   mytext replace  Z    W   print mytext

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Actually  with strings  you can do something like this   oldStr    Hello World       newStr       for i in oldStr        if  a   lt  i  lt   z               newStr    chr ord i -32           else                newStr    i print newStr    HELLO WORLD     Basically  I m  adding   strings  together into a new string

User · Answer

Python strings are immutable  you change them by making a copy  The easiest way to do what you want is probably   text    Z    text 1     The text 1   returns the string in text from position 1 to the end  positions count from 0 so  1  is the second character   edit  You can use the same string slicing technique for any part of the string  text   text  1     Z    text 2     Or if the letter only appears once you can use the search and replace technique suggested  below

[python] Changing one character in a string

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