It is necessary to understand that there are **mutable** and **immutable** data types. The first one can be changed after its creation, but the second one prohibits us from making any modifications.

```python
# Defining `variable1`
var1 = 40
# Redefining `var1`
var1 = 50
```

**Immutable** data types, as the name implies, cannot be changed once they're made.    
In contrast, **mutable** data types are objects that can be altered after they're created.



import unittest
import sys

class TestUserCode(unittest.TestCase):
    def test_var1_declared(self):
        import user_code
        self._testMethodName = 'var1 is declared'
        self.assertTrue(hasattr(user_code, 'var1'), "Expected var1 to be defined.")

    def test_var1_is_integer(self):
        self._testMethodName = 'var1 is of type int'
        import user_code
        self.assertTrue(hasattr(user_code, 'var1'), "Expected var1 to be defined.")
        self.assertIsInstance(user_code.var1, int, f"Expected var1 to be an integer, but got {type(user_code.var1).__name__}.")

    def test_var1_correct_value(self):
        self._testMethodName = 'var1 equals 150'
        import user_code
        self.assertTrue(hasattr(user_code, 'var1'), "Expected var1 to be defined.")
        self.assertEqual(user_code.var1, 150, f"Expected var1 to equal 150, but got {user_code.var1}.")

if __name__ == '__main__':
    unittest.main()

test_main.py

This course is going to help you dive deeper into data types and try to work with them. Here you will learn basic operations and all ins and outs of numbers, boolean data type, and strings. This course consists of a lot of practical tasks after which you will become a skillful programmer.

Numeric data types are crucial in Python, so it is important to start with them. Here you will work with simple math operations and find out the purposes of learning different types of numerical data.

The main goal of this section is to clarify the boolean data types; it's a sub type of numeric data, but indeed it is more challenging. Since it is always better to excel in the more difficult topics, this section is a valuable part of your curriculum.

Strings are a way for us to implement your phrases in Python, that is, to give instructions to users who are the target audience of your program. Indeed, it is always better to be able to work with strings because they should be used in your code. You'll understand why soon.

This chapter consists of practical tasks that combine all the examined topics together with a bit of theory.

Data Types in Python

Mutable or Immutable?

Solution

Mutable or Immutable?

Solution