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Python学习day09 - Python进阶（3）异常处理 1. 什么是异常 2. 语法错误 3. 逻辑错误 4. 万能捕捉异常的方式 Python深浅拷贝 1. 拷贝（赋值）2. 浅拷贝 3. 深拷贝基本的文件操作 1. 找到文件路径 2. 双击打开 3. 看文件 4. 写文件 5. 关闭文件实战之猜年龄游戏

Python学习day09 - Python进阶（3）

异常处理

1. 什么是异常

异常其实就是我们平时写程序运行程序时的报错，在Python中，异常一般分为两类，即语法错误和逻辑错误

2. 语法错误

语法错误过不了python解释器的语法检测，所以在程序执行之前必须改正，否则程序无法正常执行。

常见如下例：

xxxxxxxxxx

if#SyntaxError: invalid syntax

0 = 1#SyntaxError: can't assign to literal

语法错误的错误类型基本都是SyntaxError，后面是较详细的描述。

3. 逻辑错误

逻辑错误不同于语法错误的是，其错误类型比较多样。比如：

xxxxxxxxxx

# TypeError:int类型不可迭代

for i in 3:

    pass

# ValueError

num=input(">>: ") #输入hello

int(num)

# NameError

aaa

# IndexError

l=['egon','aa']

l[3]

# KeyError

dic={'name':'egon'}

dic['age']

# AttributeError

class Foo:pass

Foo.x

# ZeroDivisionError:无法完成计算

res1=1/0

res2=1+'str'

4. 万能捕捉异常的方式

当然我们捕捉异常是为了发现，并处理异常，所以这里介绍一种万能的捕获异常的方法：

xxxxxxxxxx

s1 = 'hello'

try:

    int(s1)

except Exception as e:

    print(e)

Exception可以替代所有的异常类型用来赋值输出，非常方便。而实际上现在的解释器本身的报错，定位错误的功能都挺强大的，所以用这个功能比较有限。

Python深浅拷贝

一般Python的拷贝分为以下三种，我们分别介绍,用copy之前记得加上头文件import copy.

1. 拷贝（赋值）

赋值的常见方式如下：

xxxxxxxxxx

lt = [1, 2, 3]

lt2 = lt

print(lt)

print(lt2)

lt.append(4)

print(lt)

print(lt2)

[1,2,3]

[1,2,3,4]

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上述打印结果可以看到，lt的值变化，lt2的值也会跟着变化，这就是最一般的赋值

2. 浅拷贝

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# lt2没有变化的情况

lt = [1, 2, 3]

lt2 = copy.copy(lt)

lt.append(4)

print(lt)  # [1, 2, 3, 4]

print(lt2)  # [1, 2, 3]

以上就是lt2没有跟随lt变化而变化，因为添加修改的是一个字符串，不是可变类型。

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# lt2变化的情况

lt = [1, 2, 3,[4,5,6]]

lt2 = copy.copy(lt)

lt[3].append(7)

print(lt)  # [1, 2, 3, [4,5,6,7]]

print(lt2)  # [1, 2, 3,[4,5,6]]

该例就是lt2跟随lt变化的情况，因为往里面添加的是修改一个列表，是可变的类型。

3. 深拷贝

深拷贝是最稳定的拷贝，也是对原值保留最好的，永远不会随原值改变。

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t = [1000, 2000, 3000, [4000, 5000, 6000]]

print('id(lt)',id(lt))

print('id(lt[0])', id(lt[0]))

print('id(lt[1])', id(lt[1]))

print('id(lt[2])', id(lt[2]))

print('id(lt[3])', id(lt[3]))

print('*' * 50)

lt2 = copy.deepcopy(lt)

print('id(lt2)',id(lt2))

print('id(lt2[0])', id(lt2[0]))

print('id(lt2[1])', id(lt2[1]))

print('id(lt2[2])', id(lt2[2]))

print('id(lt2[3])', id(lt2[3]))

print('*' * 50)

由以上打印结果可以看出，不管lt怎么改变，lt2都不会随之改变。

总结如下：

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# 牢记: 拷贝/浅拷贝/深拷贝 只针对可变数据类型

# 拷贝: 当lt2为lt的拷贝对象时,lt内的可变类型变化,lt2变化;lt内的不可变类型变化,lt2变化。

#浅拷贝:当lt2为lt的浅拷贝对象时,lt内的可变类型变化,lt2变化;lt内的不可变类型变化,lt2不变化

# 深拷贝: 当lt2为lt的深拷贝对象时,lt内的可变类型变化,lt2不变化;lt内的不可变类型变化,lt2不变

基本的文件操作

什么是文件呢，之前的博客中有介绍，文件其实就是操作系统提供给用户的一个虚拟单位，是用来存储数据的。那么用Python来对文件操作有以下几个常用的操作。

1. 找到文件路径

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path = r'D:\Python学习\.idea\Python学习.iml'

# python里就是这样打开文件路径的，以上这种也叫做绝对路径。相对路径可以如下表示

path = r'Python学习.iml'

#相对路径即你所执行的这个py文件的当前文件夹，会默认在这里搜索

2. 双击打开

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f = open(path,'w',encoding = 'utf8')

print(f)

# r-->只读,w-->只写，清空当前文件后写入，后面的encoding为所打开文件的编码格式

3. 看文件

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data = f.read()

print(data)

4. 写文件

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f.write('fsfda')

5. 关闭文件

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del f

f.close()

#需要注意的是，del f只是删除了解释器对文件的引用，并没有真正关闭文件，只有f.close才是真正的关闭文件

实战之猜年龄游戏

这是最近学习遇到的第一个稍有规模的代码，实现方式有很多种，以下两种仅供参考：

题目需求如下：

奖励物品存放在文件price.txt
给定年龄(随机18-60)，用户可以猜三次年龄
年龄猜对，让用户选择两次奖励
用户选择两次奖励后可以退出

常规猜年龄

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import random

age = random.randint(18, 60)  # 随机一个数字,18-60岁

count = 0  # 计数

f = open('price.txt', 'r', encoding='utf8')  # price.txt右下角为什么编码,则encoding为什么编码

price_dict = f.read()

price_dict = eval(price_dict)  # type:dict # 获取奖品字典

f.close()

price_self = dict()

while count < 3:

    count += 1

    inp_age = input('请输入你想要猜的年龄:')

    # 判断是否为纯数字

    if not inp_age.isdigit():

        print('搞事就骂你傻逼')

        continue

    inp_age = int(inp_age)

    # 筛选年龄范围

    if inp_age > 60 or inp_age < 18:

        print('好好题目,18-60岁,非诚勿扰')

        continue

    # 核心逻辑

    if age == inp_age:

        print('猜中了,请选择你的奖品')

        # 打印商品

        for k, v in price_dict.items():

            print(f'奖品编号:{k} {v}')

        # 获取奖品的两次循环

        for i in range(2):

            price_choice = input('请输入你需要的奖品编号:')

            if not price_choice.isdigit():

                print("恭喜你已经获得一次奖品,奖品为空!并且请输入正确的奖品编号!")

                continue

            price_choice = int(price_choice)

            if price_choice not in price_dict:

                print('你想多了吧!')

            else:

                price_get = price_dict[price_choice]

                print(f'恭喜中奖:{price_get}')

                if price_self.get(price_get):

                    price_self[price_get] += 1

                else:

                    price_self[price_get] = 1

        print(f'恭喜你获得以下奖品:{price_self}')

        break

    elif age > inp_age:

        print('猜小了')

    elif age < inp_age:

        print('猜大了')

    continue

抽奖式猜年龄

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import random

age = random.randint(18, 19)  # 随机一个数字,18-60岁

count = 0  # 计数

f = open('price.txt', 'r', encoding='utf8')  # price.txt右下角为什么编码,则encoding为什么编码

price_dict = f.read()

price_dict = eval(price_dict)  # type:dict # 获取奖品字典

f.close()

price_self = dict()

while count < 3:

    count += 1

    inp_age = input('请输入你想要猜的年龄:')

    # 判断是否为纯数字

    if not inp_age.isdigit():

        print('搞事就骂你傻逼')

        continue

    inp_age = int(inp_age)

    # 筛选年龄范围

    if inp_age > 60 or inp_age < 18:

        print('好好题目,18-60岁,非诚勿扰')

        continue

    # 核心逻辑

    if age == inp_age:

        print('猜中了,请选择你的奖品')

        # 打印商品

        for k, v in price_dict.items():

            print(f'奖品编号:{k} {v}')

        # 获取奖品的两次循环

        for i in range(2):

            price_y = input(f'请按"Y or y"转动转盘{chr(9803)}:').lower()

            if price_y != 'y':

                print("恭喜你已经获得一次奖品,奖品为空!并且请输入'Y or y'!")

                continue

            price_choice = random.randint(0, 10000)

            if price_choice > 0 and price_choice < 9900:

                price_choice = 6

                print('恭喜你, 下次一定有好东西!!', end=' ')

            else:

                price_choice = price_choice % 7

            if price_choice not in price_dict:

                print('你想多了吧!')

            else:

                price_get = price_dict[price_choice]

                print(f'恭喜中奖:{price_get}')

                if price_self.get(price_get):

                    price_self[price_get] += 1

                else:

                    price_self[price_get] = 1

        print(f'恭喜你获得以下奖品:{price_self}')

        break

    elif age > inp_age:

        print('猜小了')

    elif age < inp_age:

        print('猜大了')

    continue

以上内容均借鉴于恩师nick的博客，希望大家都去借鉴，关注，点赞~

https://www.cnblogs.com/nickchen121/p/10718112.html