理解Python中“==”和“is”的区别
在Python中比较值时,有两种常见的情况运算符:“==”和“是”。通常,这些运算符似乎执行相同的相等性检查。然而,两者在评估内容方面存在细微差别。
“==”和“is”运算符
值相等与对象同一性
值相等:
示例:
a = 10 b = 10 if a == b: print("Yay!") # Will print "Yay!" as 10 == 10
对象标识:
示例:
a = [1, 2, 3] b = a if a is b: print("Yay!") # Will print "Yay!" as a and b point to the same list
规则的例外
a = 100 b = 100 if a is b: print("Yay!") # Will print "Yay!" due to integer caching
a = "a" b = "a" if a is b: print("Yay!") # Will print "Yay!" as string literals are cached b = "aa" if a is b: print("Nay!") # Will not print as b is a different object
总之,“==”测试值相等性,而“is”测试对象标识。理解这种区别对于编写正确且高效的 Python 代码至关重要。
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