>>> a = [0]
>>> id(a)
4349920392

>>> b = a
>>> id(b)
4349920392

>>> b = a[:]
>>> id(b)
4349922696

>>> dir()
>>> dir(2)
['__abs__', '__add__', '__and__', '__bool__’,…]

>>> dir(dir)
['__call__', '__class__', '__delattr__’,…]

if (item in [1,2,3]):

if (item==1 or item==2 or item==3):

from pprint import pprint 
pprint(m_dict)

def append(item, x=[]):
    x.append(item)
    return x

m_list = append(1)
m_list = append(2)
print(‘m_list =’, m_list)

def append(item, x=None):
    if x is None:
        x=[]
    x.append(item)
    return x

m_list = append(1) #returns 1
m_list = append(2) #returns 2

class foo:
    def normal_call(self):
        print("normal_call")
    def call(self):
        print("first_call")
        self.call = self.normal_call

>>> y = foo()
>>> y.call()
first_call
>>> y.call()
normal_call
>>> y.call()
normal_call

>>> a = set([1,2,3,4])
>>> b = set([3,4,5,6])
>>> a | b # объединение
{1, 2, 3, 4, 5, 6}
>>> a & b # пересечение
{3, 4}
>>> a < b # подмножества
False
>>> a - b # разница
{1, 2}
>>> a ^ b # симметрическая разность
{1, 2, 5, 6}

a = [1, 2]
b = a
a = a + [3, 4]
print(‘a =’, a)
print(‘b =’, b)

a = [1, 2, 3, 4]
b = [1, 2]

a = [1, 2]
b = a
a += [3, 4]

>>> a
[1, 2, 3, 4]
>>> b
[1, 2, 3, 4]

>>> l = [[1, 2, 3], [4, 5], [6], [7, 8, 9]]
>>> sum(l, [])
[1, 2, 3, 4, 5, 6, 7, 8, 9]

from functools import reduce
from operator import add
data = [[1, 2, 3], [4, 5, 6]]
reduce(add, data)

>>> data
[1, 2, 3, 4, 5, 6]

a = 42
def func1():
    return a
 
def func2():
    a += 1
    return a

>>> func1()
42
>>> func2()
UnboundLocalError: local variable 'a' referenced before assignment

def func2()
    global a
    a += 1
    return a

>>> func2()
43