Python-сообщество

 dict =  {
        'A': 'A1', }
print(' '.join(dict.get(letter.upper(), letter) for letter in text))

 forwardTable = {
  'A': {'A2' : 'AA'}
 }
print(' '.join(dict.get(letter.upper(), letter) for letter in text))

 text = 'пример текста который изменяется'
forwardTable = {
  'a': {'A2' : 'AA'}
 }
print(' '.join(dict.get(letter.upper(), letter) for letter in text))

  
text = 'пример текста который изменяется'
forwardTable = {
  'а': {'A2' : 'AA'}
 }
 
def process(text, dict_changes):
    new_dict = {k : v2 for k, v in dict_changes.items() for k2, v2 in v.items()}
    out = ''
    for i in text:
        out += new_dict.get(i) or i
    return out
 
print(process(text, forwardTable))

 from transliterate import translit
ru_text = 'пример текста который изменяется'
text = translit(ru_text, language_code='ru', reversed=True)
print(text)
forwardTable = {
  'a': {'A2' : 'AA'}
 }
 
def process(text, forwardTable):
    new_dict = {k : v2 for k, v in forwardTable.items() for k2, v2 in v.items()}
    out = ''
    for i in text:
        out += new_dict.get(i) or i
    return out
 
print(process(text, forwardTable))