Inventory of common terms in Python

1. Note:

There is a special symbol at the beginning of the line to tell the programmer to ignore this line at runtime; making the code easier to read.

For example:

#这是一个注释 
print("hello world")  #print() 方法用于打印输出，python中最常见的一个函数

The output result is:

hello world

2. Keywords:

Have special meaning in programming language word.

For example:

#使用keyword模块，可以输出当前版本的所有关键字
import keyword　　#import() 函数用于动态加载类和函数 。如果一个模块经常变化就可以使用 import() 来动态载入。
keyword.kwlist   #在命令窗口中输出
>>> import keyword
>>> keyword.kwlist
['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif',
 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'l
ambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

3. Data type:

Divide data into different categories, and the category to which the data belongs is the data type.

Standard data types

There are six standard data types in Python3:

Number (number)

String (string)

List (list)

Tuple (tuple)

Set (set)

Dictionary (dictionary)

Six standard data types of Python3 Medium:

Immutable data (3): Number, String, Tuple;

Variable data (3): List ), Dictionary, Set.

4. Object:

A data value in Python that has 3 attributes - unique identification, data type and value.

(For example: if you want to kick a ball, the ball is an object, and the size, color, and price of the ball are the attributes of the ball.)

5.Str(string):

The data type of string.

For example:

#用type（）查看数据类型
a="abc"
print(type(a),a)
输出结果为：
<class &#39;str&#39;> abc

6. Characters:

For example: a, b, c,, 1, 2, 3 and other single symbols.

7.Int (inetrger):

The data type of integer.

For example:

a=1
# a=int("123")
print(type(a))
输出结果：
<class &#39;int&#39;>

8. Integer data:

An object whose data type is int and whose value is an integer value.

For example:

a=1
print(type(a))
输出结果：
<class &#39;int&#39;>

Related recommendations: "Python Video Tutorial"

9.Float:

Decimal (a number with a decimal point).

For example:

 s=1.0
 w=0.1
 e=8.9
 print(type(s))
 print(type(w))
 print(type(e))
 输出结果：
<class &#39;float&#39;>
<class &#39;float&#39;>
<class &#39;float&#39;>

10. Floating point number:

An object whose data type is float, the value is a decimal value.

11.Bool:

Boolean value.

12. Boolean value:

An object whose data type is bool, the value is True or False.

For example:

a=1
b=2
print(a>b)
print(a<b) 
输出结果：
False
True

13.NoneType:

The data type of the None object.

For example:

>>> print(type(None))
<class &#39;NoneType&#39;>
>>>

14.None:
The value is always None, which is used to indicate missing data or to determine whether a variable is empty. It is the only value of NoneType.

For example:

a=""
b="123"
c=34
d=False
e=[]
print(a==None)
print(b==None)
print(c==None)
print(d==None)
print(e==None)
输出结果：
False
False
False
False
False

It can be seen that from a type perspective, it is not equal to the empty string, not equal to the empty list, and not equal to False.

The correct judgment method is:

def fun():  #定义函数
    return None
a = fun()
if not a:
    print('T')
else:
    print('F')
 if a is None:
    print('T')
 else:
     print('F')
输出结果为：
T
T

15. Constant:

A value that will never change. (Including numbers, strings, Boolean values, and empty values. For example, the value of the number 1 is always 1)

For example:

#python内置常量
['True'、'False'、'None'、'NotImplemented'、'Ellipsis'、'__debug__']

16. Variable:

You can use the assignment character "=" to perform the value assignment operation, and can be used to save any data type.

For example:

a=1, a is the name of the variable, and 1 is the value of the variable.

int q
q=123
b=0
print(b)
>>0
x=100
print(x)
x=200
print(x)
>>100
>>200

hi="你好"
a="asd"
print(a)
print(hi)
>>asd
>>你好

Note:

1. Variable names cannot contain spaces.

　2. Variable names can only use specific letters, numbers and underscores.

　3. Variable names cannot start with numbers.

　4. Keywords cannot be used as variable names

#以下属于python内置函数，不能设为变量
['and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 
'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 
'try', 'while', 'with', 'yield']

17. Assignment operator:
“=", defines a new value for a variable.

For example:

a="你好”
print(a)
输出结果：
你好

18. Increase:
Increase the value of a variable.

For example:

a=1
a=a+1
print(a)
>>2
   或：
x=1
x+=1
print(x)
>>2

19. Reduce:

Reduce the value of a variable.

For example:

s=2
s=s-1
print(s)
>>1
或：
x=1
x-=1
print(x)
>>0

20. Grammar:

The specification of language, a set of rules and processes for the order of words in a sentence.                         

21. Syntax error:

A fatal programming error caused by violating the grammar of the language.

22. Exception:

Non-fatal programming error.

23. Operator:

Symbols used with operators when expressing.                                                                                                                                                                                                                                             

24. Arithmetic operators:

A type of operator in mathematical expressions. Such as: addition, subtraction, multiplication, division                                                                            

#偶数
12%2
>>0
#奇数
11%2
>>1

25. Operands:
The values ​​on both sides of the operator.                                                                                                         

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