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Python: The immutability of primitive types

Imagine that we need to change a character in a string. This is what will come out of it:

first_name = 'Alexander'
first_name[0] = 'B'
# Error: TypeError: 'str' object does not support item assignment

This happens because of the immutability of primitive types in Python - the language does not give any physical possibility to change the string. The immutability of primitive types is important for many reasons. The key reason is performance.

But sometimes we need to change a string. That's what variables are for:

first_name = 'Alexander'
first_name = 'Blexander'
print(first_name)  # => Blexander

There is a big difference between changing the value of a variable and changing the value itself. You can't change primitive types in Python, but you can change composite types. You can also change the value of a variable without any problem.


You are given three variables with the names of different people. Make and display a word of characters in this order:

  1. The third character from the first line
  2. The second character from the second line
  3. The fourth character from the third line
  4. The fifth character of the second line
  5. The third character from the second line

Try using interpolation: not only whole variables can be placed inside curly brackets, but also individual characters using square brackets.

The exercise doesn't pass checking. What to do? 😶

If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:

  • Be sure to attach the test output, without it it's almost impossible to figure out what went wrong, even if you show your code. It's complicated for developers to execute code in their heads, but having a mistake before their eyes most probably will be helpful.
In my environment the code works, but not here 🤨

Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.

My code is different from the teacher's one 🤔

It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.

In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.

I've read the lessons but nothing is clear 🙄

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