a = [[1, 2], [3, 4]]
b = list(a)
a[0][1] = 5
print(b[0][1])

for i in range(2):
    try:
        print(i, end="")
        continue
    finally:
        print("F", end="")

lst = [x for x in range(10) if x % 2 == 0 if x % 3 == 0]
print(lst)

colors = ['red', 'green', 'blue']
colors.insert(1, colors.pop())
colors.reverse()
print(colors[0])

class Model:
    val = 1
    lst = [val for _ in range(3)]

print(Model.lst)

data = {}
data.setdefault("keys", []).append(1)
data.setdefault("keys", []).append(2)
print(data["keys"])

class A:
    x = 1

class B(A):
    pass

class C(A):
    pass

B.x = 2
A.x = 3

print(C.x)

def make_counter():
    count = 0
    def increment():
        nonlocal count
        count += 1
        return count
    return increment

c1 = make_counter()
c2 = make_counter()
c1()
print(c1(), c2())

from collections import defaultdict

class Tree(defaultdict):
    def __init__(self):
        super().__init__(Tree)

t = Tree()
t['a']['b']['c'] = 10
t['a']['b']['d'] = 20
t['a']['e'] = 5

def count_leaves(d):
    total = 0
    for v in d.values():
        if isinstance(v, dict):
            total += count_leaves(v)
        else:
            total += v
    return total

print(count_leaves(t))

d = {'a': 1, 'b': 2, 'c': 3}
try:
    for k in d:
        del d[k]
    print(len(d))
except RuntimeError:
    print("RuntimeError")