what_is_new_36.txt

Underscore in numeric literals
==============================

print(1_000_000)  # 1000000
print(0x_FF_FF_FF_FF)  # 4294967295



f-string, formatted string
==========================
https://docs.python.org/3.7/library/string.html#formatstrings

number = 5
print(f'I have {number} apples')  # I have 5 apples

number = 123.456789
print(f'{number:07.2f}')  # 0123.46 sum 7 characters, zero padded, 2 decimals

number = 2/3
print(f'{number:5.2%}')  # 66.67% sum 5 characters, percentage with 2 decimals

big_number = 123456789
print(f'{big_number:_}')  # 123_456_789

big_hex = 0xdeadbeef
print(f'{big_hex:_x}')  # dead_beef

width = 10
precision = 4
value = 12.34567
print(f"result: {value:0{width}.{precision}}")  # 0000012.35  zero padded
print(f"result: {value:{width}.{precision}}")   #      12.35  space padded
# width and precision read from variables


Variable annotations
====================
https://docs.python.org/3/library/typing.html

Function annotation exists from 3.0

number :int = 5

numbers :list = list()

from typing import List
numbers :List[int] = list()



Simpler subclass init / creation
================================
https://docs.python.org/3.6/reference/datamodel.html#object.__init_subclass__

class Apple:
    def __init__(self):
        print('Apple init is executed')

    def __init_subclass__(cls):
        print('Class Apple is subclassed')
        print(f'Created subclass is {cls.__name__}')

class GreenApple(Apple):
    pass

my_apple = GreenApple()  # Apple's init will be called only here

==>
Class Apple is subclassed
Created subclass is GreenApple
Apple init is executed

You do not have to call super's init, in the subclass,
it can be implemented in super


pathlib - Object-oriented filesystem
====================================
https://docs.python.org/3.7/library/pathlib.html#module-pathlib

The module created in 3.4, but right now it is used by several functions



Others
======

Decimal('-3.14').as_integer_ratio()  # (-157, 50)