Replacing instances of a character in a string

Question

This simple code that simply tries to replace semicolons (at i-specified postions) by colons does not work:

for i in range(0,len(line)):
     if (line[i]==";" and i in rightindexarray):
         line[i]=":"

It gives the error

line[i]=":"
TypeError: 'str' object does not support item assignment

How can I work around this to replace the semicolons by colons? Using replace does not work as that function takes no index- there might be some semicolons I do not want to replace.

Example

In the string I might have any number of semicolons, eg "Hei der! ; Hello there ;!;"

I know which ones I want to replace (I have their index in the string). Using replace does not work as I'm not able to use an index with it.

Answer 1

To replace a character at a specific index, the function is as follows:

def replace_char(s , n , c):
    n-=1
    s = s[0:n] + s[n:n+1].replace(s[n] , c) + s[n+1:]
    return s

where s is a string, n is index and c is a character.

Answer 2

Turn the string into a list; then you can change the characters individually. Then you can put it back together with .join:

s = 'a;b;c;d'
slist = list(s)
for i, c in enumerate(slist):
    if slist[i] == ';' and 0 <= i <= 3: # only replaces semicolons in the first part of the text
        slist[i] = ':'
s = ''.join(slist)
print s # prints a:b:c;d

Answer 3

Strings in python are immutable, so you cannot treat them as a list and assign to indices.

Use .replace() instead:

line = line.replace(';', ':')

If you need to replace only certain semicolons, you'll need to be more specific. You could use slicing to isolate the section of the string to replace in:

line = line[:10].replace(';', ':') + line[10:]

That'll replace all semi-colons in the first 10 characters of the string.

Answer 4

If you want to replace a single semicolon:

for i in range(0,len(line)):
 if (line[i]==";"):
     line = line[:i] + ":" + line[i+1:]

Havent tested it though.

Answer 5

You cannot simply assign value to a character in the string. Use this method to replace value of a particular character:

name = "India"
result=name .replace("d",'*')

Output: In*ia

Also, if you want to replace say * for all the occurrences of the first character except the first character, eg. string = babble output = ba**le

Code:

name = "babble"
front= name [0:1]
fromSecondCharacter = name [1:]
back=fromSecondCharacter.replace(front,'*')
return front+back

Answer 6

How about this:

sentence = 'After 1500 years of that thinking surpressed'

sentence = sentence.lower()

def removeLetter(text,char):

    result = ''
    for c in text:
        if c != char:
            result += c
    return text.replace(char,'*')
text = removeLetter(sentence,'a')