Simple syntax for first knowledge of Python

Grammatical features:

First, the statement is more flexible

No need to declare data type, directly define variable name = variable Value

Ii. Types of data

A variable does not have a data type defined, but it has a data type.

1. Steps for Variables

1) define variable names and assign values

eg: name = ' Zhang San '

Note :

2), there is no semicolon after the statement ";", a line can only write one statement.

3), Python syntax does not have curly braces, by indentation ( The distance of a tab key ) to distinguish the hierarchical relationship between the code

Eg: "If ()

"Print ()

Print () here indicates the output (a variable name can also be output when a variable needs to be output, no print required)

2, the naming specification, and Java Almost, first can not use the key, second can not be used $, class name Capital (Karpasia), function lowercase, variable lowercase start (hump naming)

3, Python case sensitive, the name can not start the number, special symbols can only use "_"

4, How do I know what data type my variable is ? What are the data types?

Know the data type:

Type ( variable name ) Gets the variable memory address function

Id ( variable name ) returns memory address

Python 's memory mechanism:

Edge processing edges reclaim memory, when variables are re-assigned, or useless, memory space is recycled

What are the data types ?

1), String

string conversion function : str ( numeric )

STR string using "" or "package, can be nested with each other

Characteristics

Python 's escape character is the same as Java

"R" refers to a natural string, that is, anything inside a string is executed as a string (either an escape character or something)

String cannot be spliced with numbers

2), Plastic

Int, can only put integers

Most approximately 2147400000

min. approx .-2147400000

3), long plastic

A long integer larger than int

num=-2140000000 until num = 2140000000 is of type int
Starting with num = 2140000001 is the long type

The last number overrides the previous number

4), floating-point type

float, decimal

5), Boolean type

BOOL Type

Ture,false

Three, operator

1, assignment operation:=

arithmetic Operations : +-*/( fetch )%

Dividend divided by divisor = quotient ... . remainder,

Self-operation: no + +,--(only num + = 1,num *= 2,num/= 2,num%= 2,num-= 2)

2, relational operations

> ,< ,>=, <=, ! =, ==

3, logical operation

and ,or, not

4, power operation

sum = num**4 num 4-Time Square

Eg: "Num=2**4

"Print num

16

Four, Process Control statements

Basic CONDITION Statement:

If condition (bool value) :

Output statement

Else

Output statement

Eg: "score=90

if (score>=85):

"Print" Dad doesn't hit you! ”

"Else:

"Print" Go home to kneel durian! ”

Dad won't hit you!

Five, Python notes

Two kinds of

1) Single-line comment # comment (requires comment class before adding well number)

2) Multi-line comment ' ' annotation ' (need to add three single quotes before and after the comment class)

Simple syntax for first knowledge of Python