day1-python基础

Hello world 程序

　　执行代码如下，并保存hello.py文件，在linux下执行

[oracle@dbadg ~]$ cat hello.py
print("Hello world!")
[oracle@dbadg ~]$ python hello.py
Hello world!

　　在交互器中执行

C:WINDOWSsystem32>python
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello world!")
Hello world!
>>>

变量：用于存储信息

 　　变量声明：变量名为name，变量名name值为：“chx”

name = "chx"

 　　变量命名规则：

1. 变量名只能是 字母、数字或下划线的任意组合
2. 变量名的第一个字符不能是数字
3. 以下关键字不能声明为变量名
   ['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']

　　变量的赋值

name = "chx"
name2 = name

print (name,name2)

name = "jack"
print(name,name2)   #name2还会是chx，因为name2实际是通过name指向chx，而不是指向name

注释

　　单行注释：#被注释内容

#name = "chx"

　　多行注释："""被注释内容 """

1 """
2 name2 = name
3 
4 print (name,name2)
5 
6 name = "jack"
7 print(name,name2)
8 """

用户输入

name = input("what's your name ?")
print("Hello" + name)

　　密码不可见

#需要用到getpass模块
import getpass
#将值赋予pwd变量
pwd = getpass.getpass("请输入密码：")
#打印输出内容
print(pwd )   
pycharm上不好使，交互界面可以

模块认识

　　sys

import sys
print(sys.argv) 

e:pythonday1>python hello.py ss          #当将参数导入使用
['hello.py', 'ss']

　　os

import os
os.system("dir")

e:pythonday1>python hello.py    #调用操作系统命令
 Volume in drive E is work
 Volume Serial Number is 8296-2703

 Directory of e:pythonday1

03/07/2019  02:56 PM    <DIR>          .
03/07/2019  02:56 PM    <DIR>          ..
01/23/2019  10:13 PM                74 for.py
01/23/2019  10:10 PM               540 for_age.py
03/07/2019  02:56 PM               621 hello.py
03/07/2019  02:32 PM               423 if.py
01/23/2019  09:40 PM               422 if_age.py
01/23/2019  10:15 AM               578 input.py
03/05/2019  10:14 AM               178 var.py
01/23/2019  09:16 PM               142 while.py
03/05/2019  10:27 AM               537 while_age.py
               9 File(s)          3,515 bytes
               2 Dir(s)  22,389,821,440 bytes free

　　结合使用

import os,sys
os.system(''.join(sys.argv[1:]))

e:pythonday1>python hello.py dir     #调用系统命令
 Volume in drive E is work
 Volume Serial Number is 8296-2703

 Directory of e:pythonday1

03/07/2019  02:52 PM    <DIR>          .
03/07/2019  02:52 PM    <DIR>          ..
01/23/2019  10:13 PM                74 for.py
01/23/2019  10:10 PM               540 for_age.py
03/07/2019  02:52 PM               559 hello.py
03/07/2019  02:32 PM               423 if.py
01/23/2019  09:40 PM               422 if_age.py
01/23/2019  10:15 AM               578 input.py

表达式if ... else

　　场景一、用户密码登录

#输入用户名密码
#用户密码错误，提示用户密码错误
#正确，提示欢迎，XX
import getpass
name = "chx"
password = "123"
_name = input("用户名：")
#_passd = input("密码：")
_passd = getpass.getpass("密码：")
if _name == name and _passd == password:
    print("欢迎，{name} ".format(name=_name))
else:
    print("用户名或密码错误")

　　场景二、猜年龄

程序设定年龄，让程序启动起来，用户输入后根据输入的值判断，如果猜错，提示用户值大还是小

age = 24
chx_age = int(input("Guess the age of chx："))
if chx_age == age :
    print("Yes, you guessed it")
elif chx_age > age:
    print("No,think bigger..")
else:
    print("No,think smaller..")

表达式for loop

　　简单循环10次

for i in range(10):
    print("loop: ", i)
#打印出来效果
loop:  0
loop:  1
loop:  2
loop:  3
loop:  4
loop:  5
loop:  6
loop:  7
loop:  8
loop:  9

　　需求一：上面的循环，当小于5次，循环停止进入下个循环

for i in range(10):
    if i < 5:
        continue
    print("loop: ", i)



loop:  5
loop:  6
loop:  7
loop:  8
loop:  9

 　　需求二：还是上面的循环，当大于5次，循环停止退出

for i in range(10):
    if i > 5:
        break
    print("loop: ",i)

 while loop  --转载金角大王博客

　　死循环

count = 0
while True:
    print("你是风儿我是沙，缠缠绵绵到天涯.....")
    count +=1

　　上面代码循环100次退出

count = 0
while True:
    print("你是风儿我是沙，缠缠绵绵到天涯.....")
    count +=1
    if count == 100:
        print ("去你妈的风和沙,你们这些脱了裤子是人,穿上裤子是鬼的臭男人..")
        break

　　结合上面猜年龄，当猜错3次退出程序 while , for

#while loop

count = 0
age = 24
while count <3:
    chx_age = int(input("Guess the age of chx："))
    if chx_age == age:
        print("Yes,you guessed it")
        break
    elif chx_age > age:
        print("No,think bigger...")
    else:
        print("No,think smaller...")
    count +=1

#for loop

count = 0
age = 24
for i in range(3):
    chx_age = int(input("Guess the age of chx: "))
    if chx_age == age:
        print("Yes,you guessed it")
        break
    elif chx_age > age:
        print("No,think bigger...")
    else:
        print("NO,smaller...")
    count +=1