<!doctype html>day04 - 博客

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      # day04 - Python基础(2)之数据类型基础
 
 

1. 数据类型基础

什么是数据类型

  • 数据类型指的就是变量值的不同类型,姓名可能是一种数据类型、年龄可能是一种数据类型、爱好可能又是另一种数据类型,至于是什么数据类型我们将在下面详细说明。

为何对数据分类

  • 变量是用来反映事物状态以及状态变化的,所以针对不同的状态就应该用不同的数据类型去标识他。

2. 数字类型

2.1 整型

整型大多用来表示人的年龄,各种号码,级别等,也就是我们最常见的int来定义的

 
 
 
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age = 18   #age = int(18)
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print(id(age))
3
print(type(age))
4
print(age)
 
 

1527148096 <class 'int'> 18

内存空间所在地址肯定每台电脑都不一样,也就是id(age),但是同一台电脑不管重开多少次Python解释器,这个地址都是一样的。

2.2浮点型

浮点型常用来表示人的身高,体重,薪资等等。(薪资??)

 
 
 
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salary = 3.2  # salary=float(3.2)
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print(id(salary))
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print(type(salary))
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print(salary)
 
 

2569827258488 <class 'float'> 3.2

数字是我们最常见的数据类型,也是最常用的。需要注意的是,Python里如果需要用到很多数学方面公式的话,需要引入cmath模块,即在文件里加入

import math

具体模块描述可以参考以下网站

https://www.runoob.com/w3cnote/python-math-and-cmath-module.html

3. 字符串类型

字符串就是一些被串起来的字符,可以被单引号,双引号,三引号包裹。

  • 三引号包裹的优点在于字符串可以换行,但是单双引号不可以。

     
     
     
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    name1 = 'LOL'
    2
    name2 = 'DNF'
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    name3 = '''Programmers could
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    change the world'''
     
     
  • 字符串的注意事项

     
     
     
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    1
    python = 'my name is "one"'
     
     

    如果字符串内另有引号,则包裹字符串的引号与字符串内部的引号不能相同。

     
     
     
    xxxxxxxxxx
    1
     
     
     
     
    1
    print(name3[0:4])
     
     

    输出结果为

    Prog

    以上打印实际打印的是从第一个字符到第四个字符,俗称顾头不顾尾,尽管是[0:4],但打印0,1,2,3这四个字符。

    而且字符串尾部以空来表示,即

     
     
     
    xxxxxxxxxx
    1
     
     
     
     
    1
    print(name3[-4:])     # 尾部不为零,默认空,就是字符串结尾
     
     

4. 列表类型

列表的作用就是存放多个值,或者说多个字符串。

例如:

 
 
 
x
 
 
 
 
1
hobby = 'DNF'
2
hobby_list = [hobby,'LOL','FF14']
 
 

我们一直被老师强调的是就是,数据,存不是目的,取才是目的,毕竟我们把数据存起来的目的是以后用,所以我们要牢记,列表的索引序号是从0开始的。

 
 
 
xxxxxxxxxx
 
 
 
 
1
hobby_list = [hobby,'LOL','FF14']
2
# 索引序号        0    1     2 
3
print(hobby_list[1])
 
 

5. 字典类型

字典相对于列表的优点就在于,字典的存取方式是通过key:value来存取的,取得时候通过key值而不是索引去取值,key对value具有描述性的作用。存放诗句的种类各种各样并且数据交多的时候可以使用字典。

  • 字典的定义方式是在{}内用逗号分隔开多个元素,每一个元素都是key:value的格式,其中value是任意格式的数据类型,key由于具有描述性作用,所以key通常是字符串类型。
 
 
 
x
 
 
 
 
1
game_dict = {'shengda':'冒险岛',
2
             'Netease':'炉石传说',
3
             'Tencent':'DNF'}
4
 
 

取值的话就是通过key值来取值,

 
 
 
x
 
 
 
 
1
print(game_dict['Netease'])
 
 

6. 布尔类型

布尔类型的主要是用于判断条件结果,True和Flase通常情况不会直接引用,需要使用逻辑运算得到结果。

例如:

 
 
 
x
 
 
 
 
1
print(bool(0))
2
print(bool('game'))
3
print(bool(1 < 2))
4
print(bool(1 == 10))
 
 

False True True False

  • 需要注意的一点是,Python中所有数据类型的值都自带布尔值,如此多的的数据类型中我们只需要记住的就是0,None,空,False的布尔值为False,其余的均为True

7. 解压缩

解压缩类似于我们平时的压缩文件及解压缩,但有些许的不一样。

例如:

 
 
 
xxxxxxxxxx
1
 
 
 
 
1
name_list  = ['a','b','c']
2
x = y = z = name_list
3
print(f'x:{x},y:{y},z:{z}')
 
 

x:a,y:b,z:c

有一个比较巧妙的做法,就是用下划线来取值,万能的下划线可以过滤掉我们不想要的值

 
 
 
x
 
 
 
 
1
game_list = ['LOL','DNF','DN','FF14','war3','maplestory']
2
x,y,_,z,*_ = game_list
3
print(x,y,z)
4
x,*_ = game_list
5
print(x)
6
*_,z = game_list
7
print(z)
 
 

最后输出结果是

LOL DNF FF14 LOL maplestory

同样的情况字典也是适用的。

8. Python与用户交互

顾名思义,交互的意思就是我们和Python进行交流,也就是我说一句,Python回一句,说起来是个比较牛的概念,交互,实际上就是个input而已。

例如:

 
 
 
xxxxxxxxxx
1
 
 
 
 
1
print('-’*100)
2
input("请输入你的姓名:")
3
print('*'*100)
 
 
  • 此处有一个比较重要的东西就是,无论我们输入的值是数字类型,字符类型,列表类型,input的接收值都是字符串类型。所以在进行大小比对和判断的时候尤其要注意这一点,要么强制转格式,要么就在原有给定的数据格式上进行加工。

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