'str' object has no attribute 'insert'

The error message you mentioned, "'str' object has no attribute 'insert'", occurs when you try to use the `insert` method on a string object. However, the `insert` method is only available for list objects in Python.

If you want to insert a string into another string at a specific position, you can use string concatenation or string formatting instead. Here's an example:

original_str = "Hello, world!"
insert_str = "beautiful "

# Using string concatenation
new_str = original_str[:7] + insert_str + original_str[7:]
print(new_str)  # Output: Hello, beautiful world!

# Using string formatting
new_str = "{}{}{}".format(original_str[:7], insert_str, original_str[7:])
print(new_str)  # Output: Hello, beautiful world!

By slicing the original string and combining it with the insert string using concatenation or string formatting, you can achieve the desired result.