Python学习day09 - Python进阶（3）

时间：2023-08-11 17:37:08

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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：

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4
1
if#SyntaxError: invalid syntax
2
​
3
0 = 1#SyntaxError: can't assign to literal
4
​

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：

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1
# TypeError:int类型不可迭代
2
for i in 3:
3
    pass
4
​
5
# ValueError
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num=input(">>: ") #输入hello
7
int(num)
8
​
9
# NameError
10
aaa
11
​
12
# IndexError
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l=['egon','aa']
14
l[3]
15
​
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# KeyError
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dic={'name':'egon'}
18
dic['age']
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​
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# AttributeError
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class Foo:pass
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Foo.x
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​
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# ZeroDivisionError:无法完成计算
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res1=1/0
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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：

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1
s1 = 'hello'
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try:
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    int(s1)
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except Exception as e:
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    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：

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1
lt = [1, 2, 3]
2
lt2 = lt
3
print(lt)
4
print(lt2)
5
lt.append(4)
6
print(lt)
7
print(lt2)

[1,2,3]

[1,2,3]

[1,2,3,4]

[1,2,3,4]

xxxxxxxxxx
1
1
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

xxxxxxxxxx
6
1
# lt2没有变化的情况
2
lt = [1, 2, 3]
3
lt2 = copy.copy(lt)
4
lt.append(4)
5
print(lt)  # [1, 2, 3, 4]
6
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。

xxxxxxxxxx
6
1
# lt2变化的情况
2
lt = [1, 2, 3,[4,5,6]]
3
lt2 = copy.copy(lt)
4
lt[3].append(7)
5
print(lt)  # [1, 2, 3, [4,5,6,7]]
6
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。

xxxxxxxxxx
15
1
t = [1000, 2000, 3000, [4000, 5000, 6000]]
2
print('id(lt)',id(lt))
3
print('id(lt[0])', id(lt[0]))
4
print('id(lt[1])', id(lt[1]))
5
print('id(lt[2])', id(lt[2]))
6
print('id(lt[3])', id(lt[3]))
7
print('*' * 50)
8
lt2 = copy.deepcopy(lt)
9
print('id(lt2)',id(lt2))
10
print('id(lt2[0])', id(lt2[0]))
11
print('id(lt2[1])', id(lt2[1]))
12
print('id(lt2[2])', id(lt2[2]))
13
print('id(lt2[3])', id(lt2[3]))
14
print('*' * 50)
15
​

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：
xxxxxxxxxx
8
1
# 牢记: 拷贝/浅拷贝/深拷贝 只针对可变数据类型
2
​
3
# 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。
4
​
5
#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
6
​
7
# 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
8
​

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

xxxxxxxxxx
6
1
path = r'D:\Python学习\.idea\Python学习.iml'
2
​
3
# 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
4
path = r'Python学习.iml'
5
​
6
#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

xxxxxxxxxx
3
1
f = open(path,'w',encoding = 'utf8')
2
print(f)
3
# 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

xxxxxxxxxx
2
1
data = f.read()
2
print(data)

4. 写文件

xxxxxxxxxx
1
1
f.write('fsfda')

5. 关闭文件

xxxxxxxxxx
4
1
del f
2
f.close()
3
​
4
#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：

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

  • 常规猜年龄

    xxxxxxxxxx
    67
    1
    import random
    2
    ​
    3
    age = random.randint(18, 60)  # 随机一个数字,18-60岁
    4
    count = 0  # 计数
    5
    ​
    6
    f = open('price.txt', 'r', encoding='utf8')  # price.txt右下角为什么编码,则encoding为什么编码
    7
    price_dict = f.read()
    8
    price_dict = eval(price_dict)  # type:dict # 获取奖品字典
    9
    f.close()
    10
    ​
    11
    price_self = dict()
    12
    ​
    13
    while count < 3:
    14
        count += 1
    15
    ​
    16
        inp_age = input('请输入你想要猜的年龄:')
    17
    ​
    18
        # 判断是否为纯数字
    19
        if not inp_age.isdigit():
    20
            print('搞事就骂你傻逼')
    21
            continue
    22
    ​
    23
        inp_age = int(inp_age)
    24
    ​
    25
        # 筛选年龄范围
    26
        if inp_age > 60 or inp_age < 18:
    27
            print('好好题目,18-60岁,非诚勿扰')
    28
            continue
    29
    ​
    30
        # 核心逻辑
    31
        if age == inp_age:
    32
            print('猜中了,请选择你的奖品')
    33
    ​
    34
            # 打印商品
    35
            for k, v in price_dict.items():
    36
                print(f'奖品编号:{k} {v}')
    37
    ​
    38
            # 获取奖品的两次循环
    39
            for i in range(2):
    40
                price_choice = input('请输入你需要的奖品编号:')
    41
    ​
    42
                if not price_choice.isdigit():
    43
                    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!")
    44
                    continue
    45
    ​
    46
                price_choice = int(price_choice)
    47
    ​
    48
                if price_choice not in price_dict:
    49
                    print('你想多了吧!')
    50
                else:
    51
                    price_get = price_dict[price_choice]
    52
                    print(f'恭喜中奖:{price_get}')
    53
    ​
    54
                    if price_self.get(price_get):
    55
                        price_self[price_get] += 1
    56
                    else:
    57
                        price_self[price_get] = 1
    58
    ​
    59
            print(f'恭喜你获得以下奖品:{price_self}')
    60
            break
    61
    ​
    62
        elif age > inp_age:
    63
            print('猜小了')
    64
        elif age < inp_age:
    65
            print('猜大了')
    66
    ​
    67
        continue

  • 抽奖式猜年龄

    xxxxxxxxxx
    1
    74
    1
    import random
    2
    ​
    3
    age = random.randint(18, 19)  # 随机一个数字,18-60岁
    4
    count = 0  # 计数
    5
    ​
    6
    f = open('price.txt', 'r', encoding='utf8')  # price.txt右下角为什么编码,则encoding为什么编码
    7
    price_dict = f.read()
    8
    price_dict = eval(price_dict)  # type:dict # 获取奖品字典
    9
    f.close()
    10
    ​
    11
    price_self = dict()
    12
    ​
    13
    while count < 3:
    14
        count += 1
    15
    ​
    16
        inp_age = input('请输入你想要猜的年龄:')
    17
    ​
    18
        # 判断是否为纯数字
    19
        if not inp_age.isdigit():
    20
            print('搞事就骂你傻逼')
    21
            continue
    22
    ​
    23
        inp_age = int(inp_age)
    24
    ​
    25
        # 筛选年龄范围
    26
        if inp_age > 60 or inp_age < 18:
    27
            print('好好题目,18-60岁,非诚勿扰')
    28
            continue
    29
    ​
    30
        # 核心逻辑
    31
        if age == inp_age:
    32
            print('猜中了,请选择你的奖品')
    33
    ​
    34
            # 打印商品
    35
            for k, v in price_dict.items():
    36
                print(f'奖品编号:{k} {v}')
    37
    ​
    38
            # 获取奖品的两次循环
    39
            for i in range(2):
    40
                price_y = input(f'请按"Y or y"转动转盘{chr(9803)}:').lower()
    41
    ​
    42
                if price_y != 'y':
    43
                    print("恭喜你已经获得一次奖品,奖品为空!并且请输入'Y or y'!")
    44
                    continue
    45
    ​
    46
                #
    47
                price_choice = random.randint(0, 10000)
    48
    ​
    49
                if price_choice > 0 and price_choice < 9900:
    50
                    price_choice = 6
    51
                    print('恭喜你, 下次一定有好东西!!', end=' ')
    52
                else:
    53
                    price_choice = price_choice % 7
    54
    ​
    55
                if price_choice not in price_dict:
    56
                    print('你想多了吧!')
    57
                else:
    58
                    price_get = price_dict[price_choice]
    59
                    print(f'恭喜中奖:{price_get}')
    60
    ​
    61
                    if price_self.get(price_get):
    62
                        price_self[price_get] += 1
    63
                    else:
    64
                        price_self[price_get] = 1
    65
    ​
    66
            print(f'恭喜你获得以下奖品:{price_self}')
    67
            break
    68
    ​
    69
        elif age > inp_age:
    70
            print('猜小了')
    71
        elif age < inp_age:
    72
            print('猜大了')
    73
    ​
    74
        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

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