python3 函数使用 while 循环检查参数是否为 2 的幂，并且不使用数学函数

Question

学习python3中的函数。课程问题是使用 while 循环（并且不使用数学函数）定义一个函数，该函数确定参数是否为 2 的幂。如果是，则返回 True。如果不是，则返回 False。这是起始代码：

def is_power_of_two(n):
  # Check if the number can be divided by two without a remainder
  while n % 2 == 0:
    n = n / 2
  # If after dividing by two the number is 1, it's a power of two
  if n == 1:
    return True
  return False
  

print(is_power_of_two(0)) # Should be False
print(is_power_of_two(1)) # Should be True
print(is_power_of_two(8)) # Should be True
print(is_power_of_two(9)) # Should be False

我可以找到带有循环（除 while 之外）以及使用数学函数时的示例，但我在没有循环的情况下不知所措 这些选项中的任何一个。

Answer 1

n=0

是自

0 % 0 == 0

以来的一个特例。这就是为什么你有一个无限循环。

您还可以使用

return

 来简化您的 

return n == 1

语句

功能：

def is_power_of_two(n): 
    if n  == 0: 
        return False 

    while n % 2 == 0: 
        n = n / 2 

    return n == 1 

测试：

print(is_power_of_two(0)) # Should be False 
print(is_power_of_two(1)) # Should be True 
print(is_power_of_two(8)) # Should be True 
print(is_power_of_two(9)) # Should be False                                                   
print(is_power_of_two(8.1)) # Should be False

输出：

False
True
True
False
False

Answer 2

def is_power_of_two(n):
  # Check if the number can be divided by two without a remainder
  # special cases: 0, because 0 % 2 = 0
  # you can either use the n > 0 extra test below
  # if n == 0: return False # or an explicit test for zero
  while (n > 0) and (n % 2 == 0): n = n / 2
  # If after dividing by two the number is 1, it's a power of two
  return n == 1

在线示例

Answer 3

您可以使用“break”退出无限循环。

    def is_power_of_two(n):
  # Check if the number can be divided by two without a remainder
  while n % 2 == 0:
    if(n==0): break
    n = n / 2
  # If after dividing by two the number is 1, it's a power of two
  if n == 1:
    return True
  return False