替换字符串中的单个字符

Question

I am trying to make a function that automatically generated a response to a selection of an action in a text adventure game. My problem is that I have to replace every second '_' with ' '. However I have tried everything I have though of and whenever I google the question the only solution I get is to use .replace(). However .replace() replaces every instance of that character. Here is my code, could you please fix this for me and explain how you fixed it.

example_actions = ['[1] Search desk', '[2] Search Cupboard', '[3] Search yard'

def response(avaliable_actions):
    for i in avaliable_actions:
        print(i, end=' ')
        x = avaliable_actions.index(i)
        avaliable_actions[x] = avaliable_actions[x][4:]
    
    avaliable_actions = ' '.join(avaliable_actions)
    avaliable_actions = avaliable_actions.lower()

    avaliable_actions = avaliable_actions.replace(' ', '_')
    avaliable_actions = list(avaliable_actions)
    count = 0
    for i in avaliable_actions:
        if count == 2:
            count = 0
            index = avaliable_actions.index(i)
            avaliable_actions[index] = ' '
        elif i == '_':
            count += 1
            

    avaliable_actions = ' '.join(avaliable_actions)
            
    print('\n\n' + str(avaliable_actions)) #error checking

Answer 1

Did I understand you correct, that you wanna produce something like this?

this_is_a_test -> this is_a test or this_is a_test ?

If so, adapt the following for your needs:

s = "this_is_just_a_test"

def replace_every_nth_char(string, char, replace, n):
    parts = string.split(char)
    result = ""
    for i, part in enumerate(parts):
        result += part
        if i % n == 0:
            result += replace
        else:
            result += char
    return ''.join(result)

res = replace_every_nth_char(s, "_", " ", 2)
print(s, "->", res)
# "this_is_just_a_test" -> "this is_just a_test"

Answer 2

Here's one approach:

s = 'here_is_an_example_of_a_sentence'

tokens = s.split('_')
result = ' '.join('_'.join(tokens[i:i+2]) for i in range(0,len(tokens),2))
print(result)

The result:

here_is an_example of_a sentence