Python对象比较：“is”与“==”

“is”和“==”都用于Python中的对象比较。运算符“==”比较两个对象的值，而“is”检查两个对象是否相同（换句话说，两个引用相同的对象）。

# Python program to demonstrate working of 
# "=="
  
# Two different objects having same values
x1 = [10, 20, 30]
x2 = [10, 20, 30]
  
# Comparison using "==" operator
if  x1 == x2:
    print("Yes")
else:
    print("No")

输出：

Yes

“==”运算符并没有告诉我们 x1 和 x2 是否实际上指的是同一个对象。为此，我们使用“is”。

# Python program to demonstrate working of 
# "is"
  
# Two different objects having same values
x1 = [10, 20, 30]
x2 = [10, 20, 30]
  
# We get "No" here
if  x1 is x2:
    print("Yes")
else:
    print("No")
  
# It creates another reference x3 to same list.
x3 = x1
  
# So we get "Yes" here
if  x1 is x3:
    print("Yes")
else:
    print("No")
  
# "==" would also produce yes anyway
if  x1 == x3:
    print("Yes")
else:
    print("No")

输出：

No
Yes
Yes

x1 = [10, 20, 30]
  
# Here a new list x2 is created using x1
x2 = list(x1)
  
# The "==" operator would produce "Yes"
if  x1 == x2:
    print("Yes")
else:
    print("No")
  
# But "is" operator would produce "No"
if  x1 is x2:
    print("Yes")
else:
    print("No")

输出：

Yes
No

结论：

• 如果两个变量指向同一个对象，“is”返回 True。
• 如果两个变量具有相同的值（或内容），“==”返回 True。

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