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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# 函数的参数\n",
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"\n",
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"## 一、基础知识"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"#### Python 没有函数重载"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"def ff( x ): return x \n",
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"def ff( x,y ): return x + y # 同名函数后面的遮挡前面函数\n",
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"\n",
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"ff(2)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"#### 值传递和引用传递"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"# 值传递 :字符串、数字、元组 [ 不可变 ]\n",
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"\n",
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"def ff(x): x += 1 # 不改变调用值 a\n",
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"a = 5 ; ff(a) ; a"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"# 引用传递: 列表、字典 [可变]\n",
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"\n",
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"def ff(x): x.append(1) # 改变调用值 a\n",
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"a = [ 0 ] ; ff(a); a"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 二、函数参数形式\n",
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"\n",
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"Python函数的参数传递非常灵活，支持多种参数形式，使得函数定义和调用更加强大和灵活。"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 2.1 普通参数"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 位置参数\n",
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"\n",
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"位置参数是最基本的参数形式，按照它们在函数定义中的顺序传递。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Hello Alice, you are 25 years old\n"
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]
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}
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],
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"source": [
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"def greet(name, age): # name 和 age 是位置参数\n",
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" print(f\"Hello {name}, you are {age} years old\")\n",
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"\n",
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"# 调用方式\n",
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"greet(\"Alice\", 25) # 参数按照定义的顺序传入,\"Alice\" 对应 name，30 对应 age"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 默认参数\n",
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"\n",
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"为某些参数设置默认值，如果调用时不提供该参数，则使用默认值。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 17,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Hello, Bob. You are 18 years old.\n",
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"Hello, Charlie. You are 25 years old.\n"
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]
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}
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],
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"source": [
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"def greet(name, age=18):\n",
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" print(f\"Hello, {name}. You are {age} years old.\")\n",
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"\n",
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"greet(\"Bob\") # 使用默认年龄\n",
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"greet(\"Charlie\", 25) # 提供具体年龄"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 调用函数时指定参数名\n",
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"\n",
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"通过参数名进行传递，参数顺序可以任意调整，提高了代码的可读性。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 50,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Charlie 20\n",
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"Charlie 20\n",
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"Charlie 20\n",
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"Charlie 20\n"
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]
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}
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],
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"source": [
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"def greet( name,age ): print( name,age) \n",
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"\n",
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"greet( name = 'Charlie', age=20 ) # 命名传递参数,更清楚\n",
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"greet( age = 20,name = 'Charlie' ) # 顺序可以改变\n",
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"greet( 'Charlie',age = 20 ) # 混合使用,普通调用放前面,命名调用放后面\n",
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"\n",
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"name,age = 'Charlie',20 \n",
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"greet( name = name, age = age ) # 形参、实参数同名的情况"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 2.2 可变参数"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 可变位置参数 \n",
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"- 使用星号（*）定义可变数量的位置参数，这些参数被存储在一个元组中。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 18,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"6\n",
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"15\n"
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]
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}
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],
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"source": [
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"def sum_numbers(*args):\n",
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" return sum(args)\n",
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"\n",
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"# 调用方式\n",
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"print(sum_numbers(1, 2, 3)) # 输出: 6\n",
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"print(sum_numbers(1, 2, 3, 4, 5)) # 输出: 15"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 关键字参数（命名参数、字典参数）\n",
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"\n",
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"- 放在可变位置参数后面 \n",
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"- 调用的时候，必须使用名字赋值形式"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 51,
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"(1, (2, 3), 2)"
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]
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},
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"execution_count": 51,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"def ff(a,*b,c): return a,b,c\n",
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"\n",
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"ff( 1,c = 2 ) \n",
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"ff( 1,2,c = 2 )\n",
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"ff( 1,2,3,c = 2 ) "
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"# 没有可变参数，也要用 * 占位\n",
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"\n",
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"def ff(a,*,b): return a,b\n",
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"ff(1,b=2)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 52,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"1 () 0\n",
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"1 2\n",
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"1 3\n"
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]
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},
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{
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"data": {
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"text/plain": [
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"(None, None)"
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]
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},
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"execution_count": 52,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"# 有默认值的情况\n",
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"\n",
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"def ff( a,*b,c = 0 ): print(a,b,c) \n",
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"ff(1)\n",
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"\n",
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"def ff( a = 1,*, b = 2 ): print(a,b) \n",
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"ff(),ff( b = 3 ) # 前面是带默认值的位置参数"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 53,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Hello Alice, you are 25 years old\n"
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]
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}
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],
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"source": [
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"# 函数以空*开头，强制函数用关键字参数，可提升代码可读性\n",
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"\n",
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"def greet(*, name, age): # * 之后的参数只能用关键字参数\n",
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" print(f\"Hello {name}, you are {age} years old\")\n",
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"\n",
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"# 正确调用\n",
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"greet(name=\"Alice\", age=25)\n",
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"\n",
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"# 错误调用\n",
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"# greet(\"Alice\", 25) # 无 关键字命名 错误"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 可变关键字参数\n",
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"\n",
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"使用两个星号（**）定义可变数量的关键字参数。这些参数被存储在一个字典中。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 19,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"name: Eve\n",
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"age: 28\n",
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"city: London\n"
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]
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}
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],
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"source": [
|
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|
"def print_info(**kwargs):\n",
|
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|
|
" for key, value in kwargs.items():\n",
|
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" print(f\"{key}: {value}\")\n",
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"\n",
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"# 调用方式\n",
|
|
|
|
|
"print_info( name=\"Eve\", age=28, city=\"London\" )"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### 解包可变参数\n",
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"\n",
|
|
|
|
|
"在函数调用时，可以使用星号（*）或两个星号（**）来解包列表、元组或字典，将其中的元素或键值对作为参数传递给函数。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
|
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|
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"def func(a, b, *args, **kwargs):\n",
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" print(a, b, args)\n",
|
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|
|
|
" for key, value in kwargs.items():\n",
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" print(key, value)\n",
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"\n",
|
|
|
|
|
"args = (3, 4) # 或者 [\"Alice\", 25, \"Beijing\"] 其它序列容器\n",
|
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|
|
|
"kwargs = {'x': 5, 'y': 6} \n",
|
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|
|
"func(1, 2, *args, **kwargs) "
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]
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},
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{
|
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|
"cell_type": "markdown",
|
|
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|
"metadata": {},
|
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"source": [
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|
|
|
|
"## 2.3 混合使用各种参数"
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|
]
|
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},
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{
|
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|
"cell_type": "code",
|
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|
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|
"execution_count": 56,
|
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|
"metadata": {},
|
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"outputs": [
|
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|
{
|
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|
"name": "stdout",
|
|
|
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|
"output_type": "stream",
|
|
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|
|
"text": [
|
|
|
|
|
"1 () 2 {}\n",
|
|
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|
|
"1 () 2 {'d': 3}\n",
|
|
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|
|
"1 () 2 {'d': 3, 'e': 4}\n",
|
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|
|
"1 () 2 {'d': 3, 'e': 4}\n",
|
|
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|
|
"1 () 2 {'d': 3, 'e': 4}\n"
|
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|
|
]
|
|
|
|
|
}
|
|
|
|
|
],
|
|
|
|
|
"source": [
|
|
|
|
|
"# 顺序：普通参数、可变位置参数、命名参数、可变关键字参数\n",
|
|
|
|
|
"# 可变位置参数后面，命名参数选取剩下的就是可变关键字参数\n",
|
|
|
|
|
"\n",
|
|
|
|
|
"def ff( a,*b,c,**d ): print( a,b,c,d )\n",
|
|
|
|
|
"\n",
|
|
|
|
|
"ff( 1,c=2 )\n",
|
|
|
|
|
"ff( 1,c=2,d=3 )\n",
|
|
|
|
|
"ff( 1,c=2,d=3,e=4 )\n",
|
|
|
|
|
"ff( 1,d=3,e=4,c=2 )\n",
|
|
|
|
|
"ff( 1,d=3,c=2,e=4 ) # 可推测其参数确定机制"
|
|
|
|
|
]
|
|
|
|
|
},
|
|
|
|
|
{
|
|
|
|
|
"cell_type": "code",
|
|
|
|
|
"execution_count": 55,
|
|
|
|
|
"metadata": {},
|
|
|
|
|
"outputs": [
|
|
|
|
|
{
|
|
|
|
|
"name": "stdout",
|
|
|
|
|
"output_type": "stream",
|
|
|
|
|
"text": [
|
|
|
|
|
"普通参数 name : 1\n",
|
|
|
|
|
"普通参数 age : 2\n",
|
|
|
|
|
"可变参数 args : (3,)\n",
|
|
|
|
|
"命名参数 department : math\n",
|
|
|
|
|
"字典参数 kwargs : {}\n"
|
|
|
|
|
]
|
|
|
|
|
}
|
|
|
|
|
],
|
|
|
|
|
"source": [
|
|
|
|
|
"def ff( name , age ='20', *args, department = 'cs', **kwargs ): \n",
|
|
|
|
|
" '''\n",
|
|
|
|
|
" name 是必需的位置参数。\n",
|
|
|
|
|
" age 是带有默认值的位置参数。\n",
|
|
|
|
|
" *args 收集额外的位置参数。\n",
|
|
|
|
|
" **kwargs 收集额外的关键字参数。\n",
|
|
|
|
|
" ''' \n",
|
|
|
|
|
" print('普通参数 name :', name )\n",
|
|
|
|
|
" print('普通参数 age :', age )\n",
|
|
|
|
|
" print('可变参数 args :', args )\n",
|
|
|
|
|
" print('命名参数 department :', department )\n",
|
|
|
|
|
" print('字典参数 kwargs :', kwargs )\n",
|
|
|
|
|
"\n",
|
|
|
|
|
"# ff()\n",
|
|
|
|
|
"# ff(1)\n",
|
|
|
|
|
"# ff(1,2)\n",
|
|
|
|
|
"# ff(1,2,3)\n",
|
|
|
|
|
"# ff(1,2,3,4)\n",
|
|
|
|
|
"# ff(1,2,3,department='math')\n",
|
|
|
|
|
"# ff(1,2,3,u1='math')\n",
|
|
|
|
|
"# ff(1,2,3,4,5,u1='tsg',department='cmu',u2='pku' )"
|
|
|
|
|
]
|
|
|
|
|
},
|
|
|
|
|
{
|
|
|
|
|
"cell_type": "code",
|
|
|
|
|
"execution_count": null,
|
|
|
|
|
"metadata": {},
|
|
|
|
|
"outputs": [],
|
|
|
|
|
"source": [
|
|
|
|
|
"# 基础代码中常用( *args,**kwargs )参数表来抽象表示一般函数的参数\n",
|
|
|
|
|
"\n",
|
|
|
|
|
"def ff( *args,**kwargs ): \n",
|
|
|
|
|
" pass"
|
|
|
|
|
]
|
|
|
|
|
},
|
|
|
|
|
{
|
|
|
|
|
"cell_type": "markdown",
|
|
|
|
|
"metadata": {},
|
|
|
|
|
"source": [
|
|
|
|
|
"## 总结\n",
|
|
|
|
|
"\n",
|
|
|
|
|
"#### 参数顺序规则\n",
|
|
|
|
|
"<code>\n",
|
|
|
|
|
"def function(\n",
|
|
|
|
|
" 位置参数, # 普通参数\n",
|
|
|
|
|
" 默认参数 = '默认值', # 默认参数\n",
|
|
|
|
|
" *args, # 可变位置参数 \n",
|
|
|
|
|
" 关键字参数, # 普通关键字参数\n",
|
|
|
|
|
" **kwargs # 可变关键字参数\n",
|
|
|
|
|
"): pass\n",
|
|
|
|
|
"</code> \n",
|
|
|
|
|
"\n",
|
|
|
|
|
"- 可以有默认值：普通位置参数、 关键字参数"
|
|
|
|
|
]
|
|
|
|
|
}
|
|
|
|
|
],
|
|
|
|
|
"metadata": {
|
|
|
|
|
"hide_input": false,
|
|
|
|
|
"kernelspec": {
|
|
|
|
|
"display_name": "Python 3",
|
|
|
|
|
"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": "3.8.3"
|
|
|
|
|
}
|
|
|
|
|
},
|
|
|
|
|
"nbformat": 4,
|
|
|
|
|
"nbformat_minor": 4
|
|
|
|
|
}
|
