Gain insights into Python 3's new syntax, data types, strings, bytes, and iterators through interactive coding samples. Upgrade your Python skills with hands-on, real-time code modifications.

Are you ready to take the plunge into Python 3? You might be just getting started with Python or you might be someone who understands Python2 and now wants to upgrade to Python 3. This course is designed to help you achieve your goal faster.

Learn about the new syntax, data types, strings, bytes, iterators and much more with interactive coding samples. Execute code using interactive playgrounds, modify the code to see your changes in action and get yourself upgraded to the newest version of Python that is here to stay for a while.

This course is derived from Dive into Python 3 by Mark Pilgrim. See License for more details.
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Python 3: An interactive deep dive

Along with testing numbers that are too large, you need to test numbers that are too small. As [we noted in our functional requirements](https://www.educative.io/courses/python-3-an-interactive-deep-dive/not-diving-in/), Roman numerals cannot express 0 or negative numbers.

import roman2
print (roman2.to_roman(0))
#''

print (roman2.to_roman(-1))
#''

Well *that’s* not good. Let’s add tests for each of these conditions.

import unittest

class ToRomanBadInput(unittest.TestCase):
    def test_too_large(self):
        '''to_roman should fail with large input'''
        self.assertRaises(roman3.OutOfRangeError, roman3.to_roman, 4000)  #①

    def test_zero(self):
        '''to_roman should fail with 0 input'''
        self.assertRaises(roman3.OutOfRangeError, roman3.to_roman, 0)     #②

    def test_negative(self):
        '''to_roman should fail with negative input'''
        self.assertRaises(roman3.OutOfRangeError, roman3.to_roman, -1)    #③

①	The `test_too_large()` method has not changed since the previous step. I’m including it here to show where the new code fits.

②	Here’s a new test: the `test_zero()` method. Like the `test_too_large()` method, it tells the `assertRaises()` method defined in `unittest.TestCase` to call our `to_roman()` function with a parameter of 0, and check that it raises the appropriate exception, `OutOfRangeError`.

③	The `test_negative()` method is almost identical, except it passes `-1` to the `to_roman()` function. If either of these new tests does *not* raise an `OutOfRangeError` (either because the function returns an actual value, or because it raises some other exception), the test is considered failed.

Now check that the tests fail:

Your First Python Program

Native Datatypes

Comprehensions

Strings

Regular Expressions

Closures & Generators

Classes & Iterators

Advanced Iterators

Unit Testing

Refactoring

Files

XML

Serializing Python Objects

HTTP Web Services

Case Study: Porting chardet to Python 3

Packaging Python Libraries

Appendix : Where To Go From Here

More Halting, More Fire