what_is_new_38.txt

:= Assignment expression - The walrus operator
==============================================
https://docs.python.org/3.8/whatsnew/3.8.html#assignment-expressions

Note: accepting this led to Guido'd retirement as BDFL (2018-07-12)


while (block := f.read(256)) != '':
    process(block)


The equivalent code without this operator:

block = f.read(256)
while block != '':
    process(block)
    block = f.read(256)



Positional-only parameters
==========================
https://docs.python.org/3.8/whatsnew/3.8.html#positional-only-parameters

Just to know that there is such a thing.
It is not Pythonic, it is a step backward.
Simulates C language style, while they added Pythonic named arguments to C++ ...



Debug and self-documenting f-string
===================================
https://docs.python.org/3.8/whatsnew/3.8.html#f-strings-support-for-self-documenting-expressions-and-debugging

print(f'name = {name}')
== >
print(f'{name=}')

As this shortcut created for debug purposes, it will print the __repr__() value of the object
and not the __str__() value.

now = datetime.datetime.now()
print(f'{now=} {now=!s}')
now=datetime.datetime(2019, 7, 16, 16, 58, 0, 680222) now=2019-07-16 16:58:00.680222

But as the above example shows, we can use the !s modifier to print the __str__() value
The !f modifier can be used to access format parameters:

print(f'{math.pi=!f:.2f}')  # math.pi=3.14

My opinion: as usage of f-string now replaces all other
string interpolation methods, it will change in time:
will print __str__() by default



Others
======

json.tool
https://docs.python.org/3/library/json.html#module-json.tool
Add option --json-lines to parse every input line as separate JSON object.

Added new function math.dist() for computing Euclidean distance between two points

Added new function, math.prod(), as analogous function to sum()
that returns the product of a ‘start’ value (default: 1) times an iterable of numbers

Added new multiprocessing.shared_memory module

shutil.copytree() now accepts a new dirs_exist_ok keyword argument

shutil.copytree() now accepts a new dirs_exist_ok keyword argument

Added statistics.geometric_mean()

Added statistics.multimode() that returns a list of the most common values

Added statistics.quantiles() that divides data or a distribution in to
equiprobable intervals (e.g. quartiles, deciles, or percentiles)


Sped-up field lookups in collections.namedtuple().
They are now more than two times faster,
making them the fastest form of instance variable lookup in Python