Python Learning _1_ Basics

1. Naming rules 1> do not start with a number, without the Chinese name 2> without the keyword Int/pass/def/return such as 3> use letters, numbers, underscores named like class_06224> Best can see the name of the idea Str_to_list2. Variables

x = 1 y = ' hello ' #定义一个变量, and is assigned to a variable, which is a tool for storing data for later use

#在引用一个变量时, make sure that this function is defined

3. Common data types

Integer floating-point Boolean string

Aga = #整型

Score = 89.89 #浮点型

True/false #关键字Boolean BOOL Only these two

name = ' Hello ' pwd = "Fsdfs" #凡是用成对的单引号, enclosed in double quotes is the string "/" "

1> Special usage of strings

Concatenation of Strings +/,/cast

Print (a+b) #要求拼接的两边要类型一致, print () output function

Print (A, b) #对数据类型没有要求

STR (variable name/variable value) forces the contents of parentheses to be converted to STR, or to other, such as List (str), to convert STR to

　　

2> String Slice values

z = ' Hello '

The index number of the # string is starting from 0

How do I value a string? -----> string variable name [index position] z[0] #输出 h

3# take a certain value? -----> string variable name [index start position: Position at end of index +1] in Z[1:3] #输出 el

-------> Slicing left and Right (view index, easy to understand)

　　　　

' Hello ' Print (Z[2:4]) #结果为: LL Print (Z[-3:-1]) #结果为: LL　　　　
Print (z[-2:]) #取从-2 position to the last

3> formatted output

Age = 20
Sex = ' Girlprint ("The Dream Spring and autumn this year%s years old"%age)        #格式化输出
Print ("Flower this year%s years, is a% is"% (age,sex)
Print ("Flower {0} years old this year, is a {2}". Format (Age,sex)

Placeholder%s%d%f

4. Notes

1> single-line comment #

2> Multi-line comment #选中多行, CTRL +/

3> three-quote Comment

"'  Hello    python book    '

Error message:

Nameerror:name ' x ' is not defined variable X not defined

Python Learning _1_ Basics