DAY1 preview notes

Computer Basics

Computer Organization

Input and output devices CPU hard drive memory storage cards Display Power

CPU central processing various data processing equivalent to the human brain

Memory for storing data

Hard disk to store data

operating system

Control computer work flow software

application

Software installed on top of the operating system is the application

to sum up

CPU human brain

Memory person's temporary memory

The hard man of permanent memory

Operating system control computer hardware work processes

Application software is installed on top of the operating system

Introduction to Python

Applications

web development (writing Web site from scratch) Artificial Intelligence reptiles (large quantities crawling data network) Financial Analysis cloud computing

The difference Python2 and Python3

Python2 source code is not uniform repeat

Python3 no unified source code duplication

Programming language

Compiled and interpreted static and dynamic languages ​​strongly typed and weakly typed language Definition Language

Compiled

Advantages : speed fast disadvantages : slow development efficiency

Interpreted

Advantages : fast development efficiency disadvantages : running slow

Python's strengths and weaknesses

advantage

1. easy to understand

2. Development efficiency is very high, class libraries (third-party libraries) particularly

3. High-level language, regardless of the underlying details such as memory

4. Portability across platforms

5. Scalability in Python the part program is written in C or C ++

6. Embeddability, Python may be embedded in C or C ++

   Shortcoming

7. Slow

8. Code can not be encrypted

9. Thread can not take advantage of multi-CPU

Python species

Cpython（Python转C语言）    Jyhton （Python转java）  IronPython （Python转C#）

PyPy（Python转Python编译）（特殊） 

Getting Started with Python's

print()        输出

variable

print(12+34)
print((12+34)*2)
print(((12+34)\*2)*3)

a  =  12+34
b  =   a*2
c  =   b*3
print(a)    # 注意打印a的时候不能加引号

Variable rules

1. Variables are letters, numbers, underscores

2. Prohibit begin with a number

3. Prohibit the use of Python keywords

   and,as,assert,break,class,continue,def,del,elif,else,except,exec,finally,for,from,global,if,import,in,is, lanbda,not,or,pass,print,raise,return,try,while,with,yield

4. You can not use Chinese and Pinyin

5. Variable names are case-sensitive

6. Recommended wording

   CamelCase:

   Omine

   Komine

   Underline name:

   The official recommended

7. The variable name has to be descriptive

a       =        12
变量名   赋值     值

age = 18
age1 = age 
age2 = age1
age = 19

print(age,age1,age2)           #19 18 18

constant

ALEX = 2022 

Constant name in all caps

Note

Notes two ways

# Single-line comments (comment when the line) can not wrap

"" "" "" Or '' '' '' may wrap the multi-line comment

Data Types acquaintance

type (type)

Integer (int) Digital

String (str) Character 'string' 'string' '' 'string' ''

"my name is meet ,i'm 22 years ol

a = 'alex'
b = 'wusir'
print(a+b)    # alexwusir  字符串拼接   注意:只能和字符串相加

# -*-coding:utf-8 -*- 
a = '坚强'
print(a*8)    #坚强坚强坚强坚强坚强坚强坚强坚强 字符串乘   注意:只能和数字相乘

Boolean value (bool) right or wrong

True False

1 0

User interaction (input)

input Output

account password

# -*-coding:utf-8 -*-
input("提示语句")        #提示语句

# -*-coding:utf-8 -*-
s = input("请输入账号")
print(s)                # s

# -*-coding:utf-8 -*-
user = input("请输入账号:")
password = input("请输入密码:")
print(user)
print(password)         # user  password

# -*-coding:utf-8 -*-
import getpass

user = input("请输入账号:")
password = getpass.getpass("请输入密码:")
print(password)
print(user)             # 密码不可见 只能在cmd中使用

acquired digital input type

# -*-coding:utf-8 -*-
# num = input("请输入数字:")

a = 56
print(type(a))           #  class 'int'

b = 'alex'
print(type(b))           #  class 'str' 

# -*-coding:utf-8 -*-
num = input("请输入数字")

print(type(num))         #  class  'str'           由此可知,由input获取到的都是字符串

Flow control statements

if

if if

if the keyword space colon condition

Indent results

print(55)
if 3>2:
    print("你好美,小学")             #打印数字不加"", 打印汉字必须加"".
print("我说的假话")                  
#  55
   你好美,小学
   我说的假话                        #单if

if else

if else

If otherwise

if 条件:
    结果
else:
    结果

if 4>3:
    print("嗨")
else:
    print("hello")

if elif

if elif

If we if

if 条件:
    结果
elif 条件:
    结果
elif 条件:
    结果

if 3>4:
    print("真NB")
elif 5>6:
    print("更NB")
elif 3>2:
    print("稳")
elif 55>1:
    print("没毛病")          #  "稳"

if if

if 3>2:
    print(1)
if 4>3:
    print(4)
if 5>1:
    print(6)                # "1" "4" "6"

if nested

if 条件:
    结果
    if 条件:
        结果
        if 条件:
            结果

Flow control statements summary

age = int(input('请输入内容:'))    #提示语句

if age>18:
    print("可以去一些比较嗨皮的场所")
    
    if age>22:
        print("可以扯证了")
    elif 18<age<20:
        print("可以洗j")
    else:
        print("可以洗z")
        
else:
    print("兄弟,买盘吗...")                      #输入18,打印"兄弟,买盘么"     输入19,打印"可以去一些比较嗨皮的场所","可以洗j"       输入21,打印"可以去一些比较嗨皮的场所","可以洗z"