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Example 1:
      Original string:
            text = "Hello world"
      Goal: We want to replace the substring "world" with "Python".
      Python code :
            new_text = text.replace("world", "Python")
            print(new_text)
      Output string:
            Hello Python

Example 2:
      Original string:
            text = "Hello world, world is great"
      Goal: We only want to replace the first occurrence of a substring. In this case, the .replace() method takes an optional third argument, which specifies the maximum number of occurrences to replace.
      Python code:
            text = "Hello world, world is great"
            new_text = text.replace("world", "Python", 1)
            print(new_text)
      Output string:
            Hello Python, world is great
    
     
            
            

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