[FIXED] how can i replace character in a string?

Issue

hi i'm trying to simulate what the user might type for one word i.e hello so basically I have it printed out to the terminal _ _ _ _ _ and I want to replace the "_" with lets say "l" and match where it is in the string,here is my code

import re
str1="hello"
lettercheck="l"
a=re.search(lettercheck,str1)
span=(a.span())
print(span)
print(str1[span[0])
count=0
ab="_"
for char in str1:
    print(ab,end=" ")
    if lettercheck==char
    count +=1
    replacechar=str1.replace(ab,str1[span[0]])
    print(replacechar)

which prints out _ _ _ hello _ hello _ can anyone explain where I went wrong here and what can I do to fix it? note the count is just for how times how to time the letter recurrences which i will work on later on my code this is just an example to try to understand what is going on

Solution

All of the searching and replacing can be simplified. The regex library is not needed here:

str1 = 'hello'
lettercheck = "l"

positions = [pos for pos, char in enumerate(str1) if char == lettercheck]

for i in range(len(str1)):
    if i in positions:
        print(lettercheck, end='')
    else:
        print('_', end='')

returns:

__ll_

Answered By - ChrisOram