Project: Celsius to Fahrenheit

Write a program that converts a temperature from Celsius to Fahrenheit with this formula:

F = (9/5)C + 32

where F is Fahrenheit and C is Celsius. The program reads a temperature in Celsius and prints the temperature in Fahrenheit. When you run it, the output should match this format:

Please enter the temperature in Celsius.
34.5
The corresponding temperature in Fahrenheit is:
94.1

Your result only needs to match to 7 decimal places. For example, 13.0999999999 counts as correct.

In the Problem Solving lesson you worked out the expected results for 0, 100 and -40 degrees Celsius. Run your program with those three values to test it.

Save the file as temp_conversion.py.

Show a solution

Try the project on your own first. This is one working solution. Press Run, and a box asks for each input. Type the sample values from the project description to see the same output.

These tests check the solution above. They run a copy of the program, kept in PROGRAM, and give it pretend input. The testing tools here are not part of the course yet, so do not worry about how they work. Read the test names and the expected outputs: together they list what the program must do. Press Run to run the tests.

PROGRAM = r'''
print("Please enter the temperature in Celsius.")
celsius = float(input())
fahrenheit = (9 / 5) * celsius + 32
print("The corresponding temperature in Fahrenheit is:")
print(fahrenheit)
'''

# ---- Tests ----
import io
import sys
import unittest
from contextlib import redirect_stdout
from unittest import mock

def run_program(*typed_lines: str) -> str:
    """Run the program as if the user typed each line, and return what it printed."""
    answers = iter(typed_lines)

def fake_input(prompt: str = "") -> str:
        print(prompt, end="")
        return next(answers)

output = io.StringIO()
    with mock.patch("builtins.input", fake_input), redirect_stdout(output):
        exec(compile(PROGRAM.strip(), "solution.py", "exec"), {})
    return output.getvalue()

class TestCelsiusToFahrenheit(unittest.TestCase):
    def test_matches_the_sample_run_exactly(self):
        self.assertEqual(
            run_program("34.5"),
            "Please enter the temperature in Celsius.\n"
            "The corresponding temperature in Fahrenheit is:\n"
            "94.1\n",
        )

def test_freezing_point_of_water(self):
        self.assertTrue(run_program("0").endswith("is:\n32.0\n"))

def test_boiling_point_of_water(self):
        self.assertTrue(run_program("100").endswith("is:\n212.0\n"))

def test_minus_forty_is_the_same_in_both_scales(self):
        self.assertTrue(run_program("-40").endswith("is:\n-40.0\n"))

def test_negative_temperature(self):
        self.assertTrue(run_program("-10").endswith("is:\n14.0\n"))

def test_a_decimal_result_is_close_to_the_true_value(self):
        # Floating point may print 98.60000000000001, so compare with a tolerance.
        printed = run_program("37").splitlines()[-1]
        self.assertAlmostEqual(float(printed), 98.6, places=7)

# ---- Run the tests ----
loader = unittest.defaultTestLoader
suite = unittest.TestSuite(loader.loadTestsFromTestCase(case) for case in [TestCelsiusToFahrenheit])
unittest.TextTestRunner(stream=sys.stdout, verbosity=2).run(suite)

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