Transform "4CA2CACA" to "CCCCACCACA"

Question

I have already tried this (as somebody told me on another question):

 import re

 def decode(txt):
     list = []
     for cnt, char in re.findall(r"([d*])([^d])", txt):
         list.extend((char * (int(cnt) if cnt else 1)))
     list = "".join(list)
     return list

Example:

print(decode("2CACA2CACA3CACACA3CAC"))

This is what I get

CCCCCCCCCC

And this is what I need

CCACACCACACCCACACACCCAC

Asked By: vanquish

||

Source

Answer 1

What you are missing is characters without a digit in front. This will include those:

import re

def decode(txt):
    _list = []
    for cnt, char, single_char in re.findall(r"(d)([^d])|([^d])", txt):
        if single_char:
            _list.extend(single_char)
        else:
            _list.extend((char * (int(cnt) if cnt else 1)))
    _list = "".join(_list)
    return _list

print(decode("2CACA2CACA3CACACA3CAC"))

Answered By: ZerobyteHD

Answer 2

If you want to do it without any imports, then you could do something like this:

x = '2CACA2CACA3CACACA3CAC0M'
int_string = ""
char_list = []
for char in x:
    if char.isnumeric():
        int_string += char
        continue
    else:
        if not int_string:
            char_list.append(char)
        else:
            char_list.append(char * int(int_string))
        int_string = ""
print("".join(char_list))

This will work for any positive integers, even zero, as you can see in the above example.

Answered By: Hampus Larsson

Answer 3

re.sub can take a named function or lambda as its second argument, and you can use this to accomplish your goal. Using this approach you simply don’t do any substitution when a letter does not have a number in front of it.

def decode(s):
  return re.sub(r'(d+)([a-zA-Z])', 
                lambda m: m.group(2)*int(m.group(1)), 
                s)

decode("2CACA2CACA3CACACA3CAC")
# 'CCACACCACACCCACACACCCAC'

Answered By: Chris

Transform "4CA2CACA" to "CCCCACCACA"

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