lachlan-eagling

for line in open(filename):
	do_something(line)

lachlan-eagling

def basic_generator():
	for i in range(50_000_000):
    	yield i
        

gen = basic_generator()
for i in gen:
    print(i)

lachlan-eagling

def round_pows_slow():
    return [pow(x, 2) for x in range(3_000_000) if pow(x, 2) % 2 == 0]

def round_pows_fast():
    return [i for x in range(3_000_000) if (i := pow(x, 2) % 2 == 0)]

>>> round_pows_slow() runtime: 1105.8068 ms
>>> round_pows_fast() runtime: 899.7900 ms
>>> round_pows_fast() improvement: 206.0168 ms

lachlan-eagling

def round_squares_slow():
    return [pow(x, 2) for x in range(3_000_000) if pow(x, 2) % 2 == 0]

def round_squares_fast():
    return [i for x in range(3_000_000) if (i := pow(x, 2) % 2 == 0)]

>>> round_squares_slow() runtime: 1105.806827545166 ms
>>> round_squares_fast() runtime: 899.7900485992432 ms
>>> round_squares_fast() improvement: 206.01677894592285 ms

lachlan-eagling

# Scope of variable without assignment expression.
def say_hello():
    name = get_random_name()
    if name:
        print(f"Hello, {name}")
    print(f"name {name} is still in scope")

# Scope of variable using assignment expression.
def say_hello():
    if name := get_random_name():

lachlan-eagling

# Top level of an expression statement
y := f(x)

#  At the top level of the right hand side of an expression statement.
y0 = y1 := f(x)

# Value of a keyword argument in a function call.
f(x = y := f(x))

# Default value in a function definition.

lachlan-eagling

my_dict = {"age": 28}
if val := my_dict.get("name"):  # evaluates to False so `print(val)` is not executed.
	print(val)

if val := my_dict.get("age"):  # evaluates to True so `print(val)` is executed.
	print(val)

lachlan-eagling

import dis

def add(x, y):
  return x + y

>>> dis.dis(add)

2           0 LOAD_FAST                0 (x)
            2 LOAD_FAST                1 (y)
            4 BINARY_ADD

lachlan-eagling

2           0 LOAD_GLOBAL              0 (print)
            2 LOAD_CONST               1 ('Hello, World!')
            4 CALL_FUNCTION            1
            6 POP_TOP
            8 LOAD_CONST               0 (None)
            10 RETURN_VALUE

lachlan-eagling

import dis

def hello_world():
    print("Hello, World!")

>>> dis.dis(hello_world)


2           0 LOAD_GLOBAL              0 (print)
            2 LOAD_CONST               1 ('Hello, World!')