{
"cells": [
{
"cell_type": "markdown",
"id": "f40a9456",
"metadata": {},
"source": [
"# 多重继承"
]
},
{
"attachments": {},
"cell_type": "markdown",
"id": "86d9ccb1",
"metadata": {},
"source": [
"多重继承指的是一个类可以同时从多个父类继承行为与特征的功能。Python 支持多重继承的。\n",
"\n",
"例如，可以将之前的Leaf类进行抽象，树叶Leaf类，父类："
]
},
{
"cell_type": "code",
"execution_count": 1,
"id": "e0c998bd",
"metadata": {},
"outputs": [],
"source": [
"class Leaf(object):\n",
" def __init__(self, color='green'):\n",
" self.color = color"
]
},
{
"cell_type": "markdown",
"id": "0fc49c8f",
"metadata": {},
"source": [
"ColorChangingLeaf类，颜色可变的树叶，继承Leaf类："
]
},
{
"cell_type": "code",
"execution_count": 2,
"id": "1213971e",
"metadata": {},
"outputs": [],
"source": [
"class ColorChangingLeaf(Leaf):\n",
" def change(self, new_color='brown'):\n",
" self.color = new_color"
]
},
{
"cell_type": "markdown",
"id": "57e4c923",
"metadata": {},
"source": [
"DeciduousLeaf类，落叶类植物的树叶，继承Leaf类："
]
},
{
"cell_type": "code",
"execution_count": 3,
"id": "254d5547",
"metadata": {},
"outputs": [],
"source": [
"class DeciduousLeaf(Leaf):\n",
" def fall(self):\n",
" print(\"A leaf is falling!\")"
]
},
{
"cell_type": "markdown",
"id": "82908e7f",
"metadata": {},
"source": [
"MapleLeaf类，枫叶，枫叶颜色可变，同时枫树是落叶类植物，可以让它同时继承ColorChangingLeaf类和DeciduousLeaf类。"
]
},
{
"cell_type": "code",
"execution_count": 4,
"id": "15827727",
"metadata": {},
"outputs": [],
"source": [
"class MapleLeaf(ColorChangingLeaf, DeciduousLeaf):\n",
" pass"
]
},
{
"attachments": {},
"cell_type": "markdown",
"id": "e683fc72",
"metadata": {},
"source": [
"多重继承在定义时，只需要用逗号将多个父类隔开。MapleLeaf类只是简单的继承了两个类型。MapleLeaf类的对象可以使用两个父类的方法："
]
},
{
"cell_type": "code",
"execution_count": 5,
"id": "172135c2",
"metadata": {},
"outputs": [],
"source": [
"mleaf = MapleLeaf()"
]
},
{
"attachments": {},
"cell_type": "markdown",
"id": "2a8e93a0",
"metadata": {},
"source": [
"例如，从Leaf类继承而来的属性："
]
},
{
"cell_type": "code",
"execution_count": 6,
"id": "bf1d7dd9",
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"'green'"
]
},
"execution_count": 6,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"mleaf.color"
]
},
{
"attachments": {},
"cell_type": "markdown",
"id": "0a5b9445",
"metadata": {},
"source": [
"从ColorChangingLeaf类继承而来的方法："
]
},
{
"cell_type": "code",
"execution_count": 7,
"id": "aebceb2b",
"metadata": {},
"outputs": [],
"source": [
"mleaf.change(\"red\")"
]
},
{
"cell_type": "code",
"execution_count": 8,
"id": "7220d3b3",
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"'red'"
]
},
"execution_count": 8,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"mleaf.color"
]
},
{
"attachments": {},
"cell_type": "markdown",
"id": "5325fa69",
"metadata": {},
"source": [
"从DeciduousLeaf类继承而来方法："
]
},
{
"cell_type": "code",
"execution_count": 9,
"id": "c597ff5e",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"A leaf is falling!\n"
]
}
],
"source": [
"mleaf.fall()"
]
},
{
"cell_type": "markdown",
"id": "aded6105",
"metadata": {},
"source": [
"## 继承顺序"
]
},
{
"attachments": {},
"cell_type": "markdown",
"id": "18322688",
"metadata": {},
"source": [
"有时候多个父类可能会发生冲突。例如，可以在ColorChangingLeaf的定义中增加一个`.fall()`方法："
]
},
{
"cell_type": "code",
"execution_count": 10,
"id": "4bdc6d5a",
"metadata": {},
"outputs": [],
"source": [
"class ColorChangingLeaf(Leaf):\n",
" def change(self, new_color='brown'):\n",
" self.color = new_color\n",
" \n",
" def fall(self):\n",
" print(\"I am falling!!!!\")"
]
},
{
"attachments": {},
"cell_type": "markdown",
"id": "1fd50db3",
"metadata": {},
"source": [
"在两个父类的`.fall()`方法不同时，Python会优先使用定义在前的父类的方法。\n",
"\n",
"当ColorChangingLeaf类在前时，使用的是ColorChangingLeaf类的方法："
]
},
{
"cell_type": "code",
"execution_count": 11,
"id": "6d332069",
"metadata": {},
"outputs": [],
"source": [
"class MapleLeaf(ColorChangingLeaf, DeciduousLeaf):\n",
" pass"
]
},
{
"cell_type": "code",
"execution_count": 12,
"id": "f6bd05d1",
"metadata": {},
"outputs": [],
"source": [
"mleaf = MapleLeaf()"
]
},
{
"cell_type": "code",
"execution_count": 13,
"id": "c283c608",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"I am falling!!!!\n"
]
}
],
"source": [
"mleaf.fall()"
]
},
{
"cell_type": "markdown",
"id": "46a760be",
"metadata": {},
"source": [
"反过来定义时，使用的是DeciduousLeaf类的方法："
]
},
{
"cell_type": "code",
"execution_count": 14,
"id": "62525002",
"metadata": {},
"outputs": [],
"source": [
"class MapleLeaf(DeciduousLeaf, ColorChangingLeaf):\n",
" pass"
]
},
{
"cell_type": "code",
"execution_count": 15,
"id": "c8fccc73",
"metadata": {},
"outputs": [],
"source": [
"mleaf = MapleLeaf()"
]
},
{
"cell_type": "code",
"execution_count": 16,
"id": "ad1aa5ff",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"A leaf is falling!\n"
]
}
],
"source": [
"mleaf.fall()"
]
},
{
"attachments": {},
"cell_type": "markdown",
"id": "3592cac1",
"metadata": {},
"source": [
"继承的顺序可以通过该类的`.__mro__`属性或mro()方法来查看："
]
},
{
"cell_type": "code",
"execution_count": 17,
"id": "39201c5e",
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"(__main__.MapleLeaf,\n",
" __main__.DeciduousLeaf,\n",
" __main__.ColorChangingLeaf,\n",
" __main__.Leaf,\n",
" object)"
]
},
"execution_count": 17,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"MapleLeaf.__mro__"
]
},
{
"cell_type": "code",
"execution_count": 18,
"id": "c13c5538",
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"[__main__.MapleLeaf,\n",
" __main__.DeciduousLeaf,\n",
" __main__.ColorChangingLeaf,\n",
" __main__.Leaf,\n",
" object]"
]
},
"execution_count": 18,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"MapleLeaf.mro()"
]
},
{
"cell_type": "code",
"execution_count": null,
"id": "3c5be1ab",
"metadata": {},
"outputs": [],
"source": []
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 3 (ipykernel)",
"language": "python",
"name": "python3"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.9.10"
}
},
"nbformat": 4,
"nbformat_minor": 5
}