Python gcd()用法及代碼示例

最高公因子(HCF)也稱為gcd，可以使用math模塊提供的單個函數在python中進行計算，因此可以使任務在許多情況下都更輕鬆。

• 使用遞歸：

# Python code to demonstrate naive 
# method to compute gcd ( recursion ) 
  
def hcfnaive(a,b):
    if(b==0):
        return a 
    else:
        return hcfnaive(b,a%b) 
  
a = 60
b= 48
  
# prints 12 
print ("The gcd of 60 and 48 is:",end="") 
print (hcfnaive(60,48))

輸出：

The gcd of 60 and 48 is:12

1. 使用循環

   # Python code to demonstrate naive 
   # method to compute gcd ( Loops ) 
     
     
   def computeGCD(x, y):
     
       if x > y:
           small = y 
       else:
           small = x 
       for i in range(1, small+1):
           if((x % i == 0) and (y % i == 0)):
               gcd = i 
                 
       return gcd 
     
   a = 60
   b= 48
     
   # prints 12 
   print ("The gcd of 60 and 48 is:",end="") 
   print (computeGCD(60,48))

   輸出：

   The gcd of 60 and 48 is:12
   

2. 使用歐幾裏得算法

   # Python code to demonstrate naive 
   # method to compute gcd ( Euclidean algo ) 
     
     
   def computeGCD(x, y):
     
      while(y):
          x, y = y, x % y 
     
      return x 
     
   a = 60
   b= 48
     
   # prints 12 
   print ("The gcd of 60 and 48 is:",end="") 
   print (computeGCD(60,48))

   輸出：

   The gcd of 60 and 48 is:12
   

使用Python的math.gcd()函數


使用gcd()隻需一行就可以計算相同的gcd。

math.gcd( x, y )
參數：
x: Non-negative integer whose gcd has to be computed.
y:Non-negative integer whose gcd has to be computed.
返回值：
This method will return an absolute/positive integer value after 
calculating the GCD of given parameters x and y.
Exceptions:
When Both x and y are 0, function returns 0, If any number is a character ,
Type error is raised.

# Python code to demonstrate gcd() 
# method to compute gcd 
  
import math 
  
# prints 12 
print ("The gcd of 60 and 48 is:",end="") 
print (math.gcd(60,48))

輸出：

The gcd of 60 and 48 is:12

常見例外


此函數中的一些常見異常是：

• 兩個數字均為0，gcd為0
• 如果隻有一個數字不是數字，則會引發Type Error。

# Python code to demonstrate gcd() 
# method exceptions 
  
import math 
  
# prints 0 
print ("The gcd of 0 and 0 is:",end="") 
print (math.gcd(0,0)) 
  
# Produces error 
print ("The gcd of a and 13 is:",end="") 
print (math.gcd('a',13))

輸出：

The gcd of 0 and 0 is:0
The gcd of a and 13 is:

運行時錯誤：

Traceback (most recent call last):
  File "/home/94493cdfb3c8509146254862d12bcc97.py", line 12, in 
    print (math.gcd('a',13))
TypeError:'str' object cannot be interpreted as an integer