n=-15

print(n<12 and n>10, n>10 or n<0)

>>>first = 520

>>>second = '520'

>>>first = second

>>>print(type(first))

x = [1, 2, 3]

print(x.pop(1))

x = True

y = False

print(x and not y)

while True

     print("语法格式错误")

demo = []

demo.append("A","B")

print(demo)

def add(a, b=0):

     return a + b

print(add(10))

print(add(10, 20))

print(add())