Numeric type is used to store numerical values in the mathematical sense .
Number types are immutable types. The so-called immutable type means that once the value of the type is different, it is a brand new object. Numbers 1 and 2 represent two different objects respectively. Reassigning a variable to a numeric type will create a new numeric object.
A variable is just a reference to an object or a codename, name, call, etc. The variable itself has no concept of data type. Similar to 1, [2, 3, 4], only objects such as "haha" have the concept of data type.
For example:
a = 1 # 创建数字对象1。 a = 2 # 创建数字对象2，并将2赋值给变量a，a不再指向数字对象1
Here, what has changed is the point of variable a, not the number object 1 Becomes a digital object 2. Beginners may be confused, but it doesn't matter, we try to understand it. <br/>
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is usually called an integer type, which is a positive or negative integer without a decimal point. The integer type of Python3 can be used as a Long type (longer integer type), so Python3 does not have the Long type of Python2.
For example: 1, 100, -8080, 0, etc.
When representing numbers, sometimes we also use octal or hexadecimal:
Hexadecimal is prefixed with 0x And 0-9, a-f means, for example: 0xff00, 0xa5b4c3d2.
Octal is represented by 0o prefix and 0-7, such as 0o12.
Python's integer length is 32 bits, and memory space is usually allocated continuously.
空间地址（address space）表示任何一个计算机实体所占用的内存大小。比如外设、文件、服务器或者一个网络计算机。地址空间包括物理空间以及虚拟空间。
例 :
print(id(-2)) print(id(-1)) print(id(0)) print(id(1)) print(id(2))
从上面的空间地址看，地址之间正好差32。为什么会这样？
因为Python在初始化环境的时候就在内存里自动划分了一块空间，专门用于整数对象的存取。当然，这块空间也不是无限大小的，能保存的整数是有限的，所以你会看到id(0)和id(10000)之间的地址差别很大。
>>> id(0) 1456976928 >>> id(10000) 45818192
Python初始化的时候会自动建立一个小整数对象池，方便我们调用，避免后期重复生成！
这是一个包含262个指向整数对象的指针数组，范围是-5到256。也就是说比如整数10，即使我们在程序里没有创建它，其实在Python后台已经悄悄为我们创建了。
验证一下小整数对象池的存在
在程序运行时，包括Python后台自己的运行环境中，会频繁使用这一范围内的整数，如果每需要一个，你就创建一个，那么无疑会增加很多开销。创建一个一直存在，永不销毁，随用随拿的小整数对象池，无疑是个比较实惠的做法。
print(id(-6)) print(id(-5)) print(id(-4)) print(id(255)) print(id(256)) print(id(257))
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从id(-6)和id(257)的地址，我们能看出小整数对象池的范围，正好是-5到256。<br/>
除了小整数对象池，Python还有整数缓冲区的概念，也就是刚被删除的整数，不会被真正立刻删除回收，而是在后台缓冲一段时间，等待下一次的可能调用。
>>> a = 1000000>>> id(a)45818160>>> del a # 删除变量a>>> b = 1000000>>> id(b)45818160
给变量a赋值了整数1000000，看了一下它的内存地址。然后我把a删了，又创建个新变量b，依然赋值为1000000，再次看下b的内存地址，和以前a存在的是一样的。<br/>
del是Python的删除关键字，可以删除变量、函数、类等等。
这一段内容，可能感觉没什么大用，但它对于理解Python的运行机制有很大帮助。
Floating point numbers are decimals, such as 1.23, 3.14, -9.01, etc. But for very large or very small floating point numbers, they are generally expressed in scientific notation, replacing 10 with e, 1.23x10^9 is 1.23e9, or 12.3e8, 0.000012 can be written as 1.2e-5, and so on.
Complex numbers are composed of real part and imaginary part. You can use a bj, or complex(a ,b) means that the real part a and the imaginary part b of the complex number are both floating point types. Regarding complex numbers, it is usually difficult to encounter them without doing scientific calculations or other special needs.
Number type conversion:
Sometimes, we need to convert the type of numbers. Python provides us with convenient built-in data type conversion functions.
int(x): Convert x to an integer. If x is a floating point number, the decimal part is truncated.
float(x): Convert x to a floating point number.
complex(x): Convert x to a complex number, with the real part being x and the imaginary part being 0.
complex(x, y)：将 x 和 y 转换到一个复数，实数部分为 x，虚数部分为 y。
转换过程中如果出现无法转换的对象，则会抛出异常，比如int("haha")，你说我把字符串“haha”转换为哪个整数才对？
a = 10.53b = 23print(int(a)) print(float(a)) print(complex(a)) print(complex(a, b))
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科学计算需要导入math这个库，它包含了绝大多数我们可能需要的科学计算函数，一般常用的函数主要包括abs()、exp()、fabs()、max()、min()等，这里就不再赘述了，感兴趣的小伙伴可以自行百度下。
下面是两个常用数学常量：
| Constant | ##Description |
|---|---|
| pi | ##Mathematical constant pi (pi, generally expressed as π Represents) |
| e | Mathematical constant e, e is Natural constants (natural constants). |
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