python如何查找是否存在某个变量?

res1 = 'test' in locals().keys()

res2 = 'test' in dir()

res3 = 'test' in vars().keys()

print(res1,res2,res3)  # 变量test暂时还没有定义，返回False

test = ""  # 定义变量test

res4 = 'test' in locals().keys()

res5 = 'test' in dir()

res6 = 'test' in vars().keys()

print(res4,res5,res6)  # 变量test已经被定义了，返回True