Skip to main content

Python Versions

Python2 vs Python3​

  • Python 2 automatically performs integer arithmetic if both operands are integers

New in python3.7​

  1. contextvars
  2. dataclasses
  3. ordered dictionaries by default (OrderedDictpreserves the orderin which the keys are inserted. A regular dict doesn't track the insertion order, and iterating it gives the values in an arbitrary order. By contrast, the order the items are inserted is remembered by OrderedDict.)

https://docs.python.org/3/whatsnew/3.7.html

Why to move to Python3.7​

  • Fast
  • Data Classes
  • f-strings
  • dropping support
  • django support dropping for advanced versions
  • type annotations

Libraries for migrations​

  • Six-- best for adding Python 3 compatibility to your existing Python 2 code.
  • 2to3-- best for converting Python 2 code to Python 3 code.
  • Python-future-- best for those that want to focus on writing python 3 code going forward while ensuring backward compatibility with Python 2.

Must use Python 3 Features​

  1. f-strings (3.6+)

  2. Pathlib (3.4+)

  3. Type hinting (3.5+)

    def sentence_has_animal(sentence: str) -> bool:
        return "animal" in sentence

  4. Enumerations (3.4+)

  5. Built-in LRU cache (3.2+)

    Using decorator @lru_cache(maxsize=512)

  6. Extended iterable unpacking (3.0+)

  7. Data Classes (3.7+)

  8. Implicit namespace packages (3.3+)

https://datawhatnow.com/things-you-are-probably-not-using-in-python-3-but-should

Python 3.8​

Assignment Expression (Walrus operator)​

val = func1()
if not val:
    logging.warning('func1 no good')
    val = func2()
    if not val:
        logging.warning('func2 no good')
        val = func3()
if not val:
    raise ValueError('All went south')

# Do something with val after

After upgrading to 3.8, you could refactor it to:

if not (val := func1()):
    logging.warning('func1 no good')
    if not (val := func2()):
        logging.warning('func2 no good')
        if not (val := func3()):
            raise ValueError('All went south')
# Do something with val after

Positional Only Arguments​

def func(a, /):
    pass

func('foobar')
func(a='foobar') # This raises

Runtime Audit Hooks​

https://docs.python.org/3/whatsnew/3.8.html

Python 3.9​

  • Dictionary Union Operators

    a = {1: 'a', 2: 'b', 3: 'c'}
    b = {4: 'd', 5: 'e'}
    c = a | b
    print(c)
    [Out]: {1: 'a', 2: 'b', 3: 'c', 4: 'd', 5: 'e'}

    a = {1: 'a', 2: 'b', 3: 'c', 6: 'in both'}
    b = {4: 'd', 5: 'e', 6: 'but different'}
    print(a | b)
    [Out]: {1: 'a', 2: 'b', 3: 'c', 6: 'but different', 4: 'd', 5: 'e'}

  • Type Hinting

  • Two New String Methods

    "Hello world".removeprefix("He")
    "Hello world".removesuffix("ld")

  • New Python Parser

    The new parser, based on PEG, will allow the Python developers significantly more flexibility