Summary  
This chapter explains how to use Python’s built-in type() function (via printing) to inspect data types and illustrates how arithmetic operations—especially division—affect numeric types, with division always yielding a float and mixed-type operations promoting to float.  

General domain of usage  
Numeric computations

Watch this video to see how Python determines the type of a value during calculations, and how you can use the type() function to check the type of any variable. You'll learn why certain operations, like division, result in a float even when the answer looks like a whole number, and how to confidently identify and work with different number types in your code.

We've previously come across float and integer types, so now we can tell whether a value is a __float__ or an __integer__. Can you guess what the result of the math operation `6/1.5` might be? It's easy to calculate that it equals `4`, but what type does `4` belong to? It might seem like an integer, but it's actually a float. To confirm its type, you can use the `type()` function.

variable = 6/1.5
print(variable)
print(type(variable))

import unittest
from contextlib import redirect_stdout
import io
import importlib


class TestUserCode(unittest.TestCase):
    def test_number1_declared(self):
        self._testMethodName = 'number1 is declared'
        import user_code
        self.assertTrue(hasattr(user_code, 'number1'), "Expected number1 to be defined.")

    def test_number1_is_float(self):
        self._testMethodName = 'number1 is of type float'
        import user_code
        self.assertTrue(hasattr(user_code, 'number1'), "Expected number1 to be defined.")
        self.assertIsInstance(user_code.number1, float, f"Expected number1 to be a float, but got {type(user_code.number1).__name__}.")

    def test_number2_declared(self):
        self._testMethodName = 'number2 is declared'
        import user_code
        self.assertTrue(hasattr(user_code, 'number2'), "Expected number2 to be defined.")

    def test_number2_is_int(self):
        self._testMethodName = 'number2 is of type int'
        import user_code
        self.assertTrue(hasattr(user_code, 'number2'), "Expected number2 to be defined.")
        self.assertIsInstance(user_code.number2, int, f"Expected number2 to be a int, but got {type(user_code.number2).__name__}.")

    def test_type_number1_printed(self):
        self._testMethodName = "The type of number1 is <class 'float'> is printed"
        output = self._runcode_output()
        self.assertIn("number1 is <class 'float'>", output, "Expected the output to contain 'The type of number1 is <class \'float\'>'")

    def test_type_number2_printed(self):
        self._testMethodName = "The type of number2 is <class 'int'> is printed"
        output = self._runcode_output()
        self.assertIn("is <class 'int'>", output, "Expected the output to contain 'The type of number2 is <class \'float\'>'")
    
    def _runcode_output(self):
        import user_code
        f = io.StringIO()
        with redirect_stdout(f):
            importlib.reload(user_code)
        s = f.getvalue().strip()
        return s
if __name__ == '__main__':
    unittest.main()

test_main.py

A focused, beginner-friendly course on working with numbers in Python. Learn about integers, floats, arithmetic operations, type conversion, and how to avoid common pitfalls when handling numerical data.

How to Define a Type

Lösning