![](https://img-blog.csdnimg.cn/2020022320072340.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
python主要包括9中基本数据类型
- 数值类型:整数、浮点数、复数
- 字节类型:字符串、字节串
- 组合类型:集合、元祖、列表、字典
![](https://img-blog.csdnimg.cn/20200223200918444.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223201132253.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223201212649.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223201255238.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223201455526.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
为什么会出现不确定尾数?计算机
![](https://img-blog.csdnimg.cn/20200223201544607.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
不确定尾数问题来源于浮点数在计算机中表示不精确的实际情况,广泛存在于编程语言中
使用round()辅助浮点数运算,消除不确定尾数
round(0.1+0.2,1) #0.3
round(x,d) #对x四舍五入,d是小数截取位数
浮点数间运算及比较用round()函数辅助
不确定尾数一般发送在10的-16次方左右,round()非常有效。
![](https://img-blog.csdnimg.cn/20200223201746869.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223201859376.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
将浮点数转换为整数,利用整数没有尾数,并且没有取值范围的特点,来计算
![](https://img-blog.csdnimg.cn/20200223202114524.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223202247213.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223202331736.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/2020022320235656.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
数值运算函数与方法
![](https://img-blog.csdnimg.cn/20200223202519368.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223202627492.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223202705440.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223202810312.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223202857519.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
类型转换
![](https://img-blog.csdnimg.cn/20200223202952537.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223203054533.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223203119908.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200223203209769.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
64位的电脑,则就用64个0或1表示一个数,所以
![](https://img-blog.csdnimg.cn/20200224195311903.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200224195521681.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200224195606446.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200224195955754.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200224200319866.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
x+y 后字符串x和y并没有改变,它形成了新的字符串,
![](https://img-blog.csdnimg.cn/20200224200522277.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
week_str = "星期一星期二星期三星期四星期五星期六星期日"
value = input("请输入星期几:")
pos = (int(value) - 1) * 3
print(week_str[pos:pos+3])
week_str = "一二三四五六日"
value = eval( input("请输入星期几:"))
print("今天是星期{}".format(week_str[value-1:value]))#format()括号中的内容替代前面的{}
print("今天是星期"+week_str[value-1:value]) #一个切片表示,value-1这个位置的字符
![](https://img-blog.csdnimg.cn/20200224202957990.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200224211824801.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200224211938833.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/202002242120444.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/2020030817395534.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310193301931.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310193323959.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/2020031019335469.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/2020031019341254.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310193223392.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310195031203.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310195210330.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
什么时候使用字节串?
处理文本都使用的字符串。
字节串只有在处理与内存相关的内容 ,或者处理的内容与字节的数量密切相关的时候。
![](https://img-blog.csdnimg.cn/20200310195354511.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310195802341.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310195531454.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/2020031019555960.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310195831488.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310195905616.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/20200310200018738.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
![](https://img-blog.csdnimg.cn/2020031020033314.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Vzc3RtaXJhY2xl,size_16,color_FFFFFF,t_70)
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