超详解——Python 编程中的类型和对象深入探讨——基础篇

# 以下条件都为False
if not None:
    print("None is considered False")  # 输出

if not False:
    print("False is considered False")  # 输出

if not []:
    print("Empty list is considered False")  # 输出

if not 0:
    print("Zero is considered False")  # 输出

# 非零数值和非空序列为True
if 1:
    print("1 is considered True")  # 输出

if [1, 2, 3]:
    print("Non-empty list is considered True")  # 输出

user_input = input("Enter something: ")

if user_input:
    print("You entered:", user_input)
else:
    print("You didn't enter anything.")

a = [1, 2, 3]
b = a  # b引用a的同一个对象
c = [1, 2, 3]  # c创建了一个新的列表对象

print(a is b)  # True，因为a和b引用同一个对象
print(a is c)  # False，因为a和c是不同的对象，即使它们的内容相同

# 一般情况下，使用 == 来比较对象的值
print(a == c)  # True，因为a和c的内容相同

def check_value(value):
    if value is None:
        print("Value is None")
    else:
        print("Value is not None")

check_value(None)  # 输出：Value is None
check_value(0)  # 输出：Value is not None

a = 10
b = 3.14
c = "hello"

print(type(a))  # <class 'int'>
print(type(b))  # <class 'float'>
print(type(c))  # <class 'str'>

if type(a) == type(b):
    print("Same type")
else:
    print("Different types")  # 输出，因为a是int，b是float

class Animal:
    pass

class Dog(Animal):
    pass

d = Dog()

print(isinstance(d, Dog))  # True，因为d是Dog类的实例
print(isinstance(d, Animal))  # True，因为d是Animal类的子类的实例
print(isinstance(d, object))  # True，因为所有类都是object类的子类

def process_input(value):
    if isinstance(value, int):
        print(f"Processing integer: {value}")
    elif isinstance(value, float):
        print(f"Processing float: {value}")
    elif isinstance(value, str):
        print(f"Processing string: {value}")
    else:
        print("Unsupported type")

process_input(10)    # 输出：Processing integer: 10
process_input(3.14)  # 输出：Processing float: 3.14
process_input("hello")  # 输出：Processing string: hello
process_input([])    # 输出：Unsupported type

# 将字符串转换为整数
number = int("123")
print(number)  # 123

# 将整数转换为字符串
text = str(123)
print(text)  # "123"

# 创建一个包含0到4的列表
numbers_list = list(range(5))
print(numbers_list)  # [0, 1, 2, 3, 4]

# 创建一个字典
numbers_dict = dict(a=1, b=2)
print(numbers_dict)  # {'a': 1, 'b': 2}

# 创建一个集合（自动去重）
unique_numbers = set([1, 2, 2, 3, 4])
print(unique_numbers)  # {1, 2, 3, 4}

def get_user_input():
    user_input = input("Enter a number: ")
    try:
        number = int(user_input)
        print(f"You entered the integer: {number}")
    except ValueError:
        print("Invalid input. Please enter a valid integer.")

get_user_input()

int a = 10;
int *p = &a;
printf("%d", *p);  // 输出10

a = 10
b = a
print(b)  # 输出10

# 修改a的值
a = 20
print(b)  # 输出10，因为b是a的一个副本

# 使用列表来模拟指针行为
list_a = [10]
list_b = list_a
list_a[0] = 20
print(list_b[0])  # 输出20，因为list_b和list_a引用同一个列表对象

import gc

# 创建一个对象
class MyClass:
    def __init__(self, value):
        self.value = value

# 创建对象并删除引用
obj = MyClass(10)
del obj

# 强制进行垃圾回收
gc.collect()