如何确定整数是偶数还是奇数

Question

def is_odd(num):
    # Return True or False, depending on if the input number is odd. 
    # Odd numbers are 1, 3, 5, 7, and so on. 
    # Even numbers are 0, 2, 4, 6, and so on. 

我想知道你会从这里做些什么来得到那些答案.

Answer 1

def is_odd(num):
    return num & 0x1

它不是最易读的,但它很快:

In [11]: %timeit is_odd(123443112344312)
10000000 loops, best of 3: 164 ns per loop

与

def is_odd2(num):
   return num % 2 != 0

In [10]: %timeit is_odd2(123443112344312)
1000000 loops, best of 3: 267 ns per loop

或者,使返回值与以下相同is_odd:

def is_odd3(num):
   return num % 2

In [21]: %timeit is_odd3(123443112344312)
1000000 loops, best of 3: 205 ns per loop

Answer 2

def is_odd(num):
   return num % 2 != 0

符号"%"被称为模数,并返回一个数的除法的余数.