<gh_stars>1-10
nums = []
print(len(nums))
print(not nums)

nums = [1,3,4,5,2]
nums.sort()
print(nums)

print(1^2)

stack =[]
stack.append(1)
print(stack)
stack.append(2)
print(stack)
stack.pop() # 意思是stack.pop(index = -1)
print(stack)
nums = []
print(len(nums))
print(not nums)

nums = [1,3,4,5,2]
nums.sort()
print(nums)

print(1^2)

stack =[]
stack.append(1)
print(stack)
stack.append(2)
print(stack)
stack.pop() # 意思是stack.pop(index = -1)
print(stack)
# 意思是stack.pop(index = -1)