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

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

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))

a = 256
b = 256
c = 257
d = 257
print(a is b, c is d)

def f(x, y, z):
    return x + y + z

d1 = {'x': 1, 'y': 2}
d2 = {'y': 3, 'z': 4}

try:
    print(f(**d1, **d2))
except TypeError:
    print("TypeError")

class MetaClass(type):
    def __new__(cls, name, bases, dct):
        dct['meta_value'] = 100
        return super().__new__(cls, name, bases, dct)
    
    def __init__(cls, name, bases, dct):
        cls.meta_value += len(name)

class A(metaclass=MetaClass):
    pass

class B(metaclass=MetaClass):
    pass

print(A.meta_value + B.meta_value)

def modify(n):
    n = n + 5
    n *= 2
    return n

x = 10
result = modify(x) + x
print(result)