January 30, 2026

类型检查示例

本文档介绍 type() 与 isinstance() 的用法。示例来源：doc/pikapython.com/examples/builtins/。

模块简介

支持 type(obj) 获取类型、isinstance(obj, class) 判断实例关系。内嵌示例：

assert type(1) == int
assert isinstance('a', str)

示例代码

type 函数（type.py）

class Test1:
    def test(self):
        return 'test 1'


class Test2:
    def test(self):
        return 'test 2'

t1 = Test1()
tt1 = type(t1)
ttt1 = tt1()

t2 = Test2()
tt2 = type(t2)
ttt2 = tt2()

assert ttt1.test() == 'test 1'
assert ttt2.test() == 'test 2'
assert type(ttt1) == Test1
assert type(ttt2) == Test2
assert type(ttt1) != type(ttt2)
assert type(ttt1) != Test2
assert type(ttt2) != Test1

print('PASS')

说明：type(实例) 得到类对象，该类对象可再次调用以创建新实例；用 == 比较类型是否相同。

isinstance 检查（isinstance.py）

# Testing with builtin types
assert isinstance(10, int) == True
assert isinstance("Hello, world!", str) == True
assert isinstance([1, 2, 3, 4, 5], list) == True
assert isinstance({"key": "value"}, dict) == True
assert isinstance(3.14, float) == True
assert isinstance(object(), object) == True
assert isinstance(10, str) == False

class MyClass:
    pass

class BaseClass(object):
    def __init__(self):
        self.a = 1

class DerivedClass(BaseClass):
    def __init__(self):
        super().__init__()
        self.b = 2

base_instance = BaseClass()
derived_instance = DerivedClass()

# Instances of DerivedClass should also be instances of BaseClass
assert isinstance(MyClass(), object) == True
assert isinstance(base_instance, object) == True
assert isinstance(base_instance, BaseClass) == True
assert isinstance(derived_instance, BaseClass) == True

# However, instances of BaseClass are not instances of DerivedClass
assert isinstance(base_instance, DerivedClass) == False

# And instances of DerivedClass are, of course, instances of DerivedClass
assert isinstance(derived_instance, DerivedClass) == True

print('PASS')

说明：isinstance(obj, Class) 对内置类型和继承关系均有效，子类实例对基类返回 True。

isinstance 在逻辑分支中的使用（issue_isinstance.py）

class scr_Text:
    def cus_print(self, data, end='\n'):
        str_buf = ""

        if isinstance(data, str):
            str_buf = str_buf + data
        elif isinstance(data, int):
            str_buf = str_buf + str(data)
        else:
            str_buf = "The type is not recognized"
        str_buf = str_buf + end


screen = scr_Text()
screen.cus_print(12)
screen.cus_print(12)
screen.cus_print(12)
screen.cus_print(12)

print('PASS')

说明：根据 isinstance 分支处理不同数据类型，实现简单多态或格式化输出。

注意事项

用 type(x) == Type 只判断精确类型，不包含子类；若需考虑继承，宜用 isinstance(x, Type)。
在 OPBTPython 中，内置类型与 PikaPython 文档保持一致，行为可能与 CPython 有细微差异。