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

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

　　在交互器中执行

1 C:WINDOWSsystem32>python
2 Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
3 Type "help", "copyright", "credits" or "license" for more information.
4 >>> print("Hello world!")
5 Hello world!
6 >>>

变量：用于存储信息

　　变量声明：变量名为name，变量名name值为：“chx”

1 name = "chx"

　　变量命名规则：

变量名只能是字母、数字或下划线的任意组合
变量名的第一个字符不能是数字
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

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

1 #name = "chx"

　　多行注释："""被注释内容 """

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

用户输入

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

　　密码不可见

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

模块认识

　　sys

1 import sys
2 print(sys.argv) 
3 
4 e:pythonday1>python hello.py ss          #当将参数导入使用
5 ['hello.py', 'ss']

 1 import os
 2 os.system("dir")
 3 
 4 e:pythonday1>python hello.py    #调用操作系统命令
 5  Volume in drive E is work
 6  Volume Serial Number is 8296-2703
 7 
 8  Directory of e:pythonday1
 9 
10 03/07/2019  02:56 PM    <DIR>          .
11 03/07/2019  02:56 PM    <DIR>          ..
12 01/23/2019  10:13 PM                74 for.py
13 01/23/2019  10:10 PM               540 for_age.py
14 03/07/2019  02:56 PM               621 hello.py
15 03/07/2019  02:32 PM               423 if.py
16 01/23/2019  09:40 PM               422 if_age.py
17 01/23/2019  10:15 AM               578 input.py
18 03/05/2019  10:14 AM               178 var.py
19 01/23/2019  09:16 PM               142 while.py
20 03/05/2019  10:27 AM               537 while_age.py
21                9 File(s)          3,515 bytes
22                2 Dir(s)  22,389,821,440 bytes free

　　结合使用

 1 import os,sys
 2 os.system(''.join(sys.argv[1:]))
 3 
 4 e:pythonday1>python hello.py dir     #调用系统命令
 5  Volume in drive E is work
 6  Volume Serial Number is 8296-2703
 7 
 8  Directory of e:pythonday1
 9 
10 03/07/2019  02:52 PM    <DIR>          .
11 03/07/2019  02:52 PM    <DIR>          ..
12 01/23/2019  10:13 PM                74 for.py
13 01/23/2019  10:10 PM               540 for_age.py
14 03/07/2019  02:52 PM               559 hello.py
15 03/07/2019  02:32 PM               423 if.py
16 01/23/2019  09:40 PM               422 if_age.py
17 01/23/2019  10:15 AM               578 input.py

表达式if ... else

　　场景一、用户密码登录

 1 #输入用户名密码
 2 #用户密码错误，提示用户密码错误
 3 #正确，提示欢迎，XX
 4 import getpass
 5 name = "chx"
 6 password = "123"
 7 _name = input("用户名：")
 8 #_passd = input("密码：")
 9 _passd = getpass.getpass("密码：")
10 if _name == name and _passd == password:
11     print("欢迎，{name} ".format(name=_name))
12 else:
13     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

1 age = 24
2 chx_age = int(input("Guess the age of chx："))
3 if chx_age == age :
4     print("Yes, you guessed it")
5 elif chx_age > age:
6     print("No,think bigger..")
7 else:
8     print("No,think smaller..")

表达式for loop

　　简单循环10次

 1 for i in range(10):
 2     print("loop: ", i)
 3 #打印出来效果
 4 loop:  0
 5 loop:  1
 6 loop:  2
 7 loop:  3
 8 loop:  4
 9 loop:  5
10 loop:  6
11 loop:  7
12 loop:  8
13 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

 1 for i in range(10):
 2     if i < 5:
 3         continue
 4     print("loop: ", i)
 5 
 6 
 7 
 8 loop:  5
 9 loop:  6
10 loop:  7
11 loop:  8
12 loop:  9

　　需求二：还是上面的循环，当大于5次，循环停止退出

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

while loop --转载金角大王博客

　　死循环

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

　　上面代码循环100次退出

1 count = 0
2 while True:
3     print("你是风儿我是沙，缠缠绵绵到天涯.....")
4     count +=1
5     if count == 100:
6         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..")
7         break

　　结合上面猜年龄，当猜错3次退出程序 while , for

 1 #while loop
 2 
 3 count = 0
 4 age = 24
 5 while count <3:
 6     chx_age = int(input("Guess the age of chx："))
 7     if chx_age == age:
 8         print("Yes,you guessed it")
 9         break
10     elif chx_age > age:
11         print("No,think bigger...")
12     else:
13         print("No,think smaller...")
14     count +=1
15 
16 #for loop
17 
18 count = 0
19 age = 24
20 for i in range(3):
21     chx_age = int(input("Guess the age of chx: "))
22     if chx_age == age:
23         print("Yes,you guessed it")
24         break
25     elif chx_age > age:
26         print("No,think bigger...")
27     else:
28         print("NO,smaller...")
29     count +=1