Day01 - Python基础1

Day01的课程要点记录
详细教程地址：金角大王 - Day1 Python基础1 | 银角大王 - 初始Python

一、我能学会吗？

Can I become a great coder?
Yes - in time. The best coders go through several phases on their programming journey:

1. The "I know nothing" phase - 起始阶段
   Everything is new, nothing is easy.
2. The "it's starting to make sense" phase -
   You're written a few programs and are making fewer mistakes.
3. The "I'm invincible" phase - 第三个月到第五个月
   Your confindence matches your competence. No challenge seems to difficult.
4. The "I know nothing" phase,part II - 项目实战
   The sudden realization that development is infinitely more complex and you begin to doubt your own abilities.
5. The "I know a bit and that's OK" phase - 四、五年开发经验
   You have decent coding skills but recognize your limitations and can find solutions to most problems (even if that means hiring another developer).

二、2与3的选择

语法区别

#2.x
print “hello world”

#3.x
print("hello")

2.x 汉字需要声明

#_*_coding:utf-8_*_

三、Python安装

• Windows

1、下载安装包
    https://www.python.org/downloads/
2、安装
    默认安装路径：C:\python27
3、配置环境变量
    【右键计算机】-->【属性】-->【高级系统设置】-->【高级】-->【环境变量】-->【在第二个内容框中找到 变量名为Path 的一行，双击】 --> 【Python安装目录追加到变值值中，用 ;分割】
    如：原来的值;C:\python27，切记前面有分号

• Linux、Mac

无需安装，原装Python环境
ps：如果自带2.6，请更新至2.7

四、Python入门

• Hello World程序

print("Hello World!")

• 在Linux下运行

print("Hello World!")
print("Hello Again.")
print("hello again \ntwice") #\n 为换行

#检查是否有可执行权限
ll hello.py (Mac: ls -slh)
#添加可执行权限
chmod +x hello.py #方法1
chmod 755 hello.py #方法2

#指定解释器 - 在文件第一行添加
#!/usr/bin/python (不推荐)
#!/usr/bin/env python (推荐)

• 注意点

1. 带有引号的（‘ "），无论几个，都代表是字符串。
2. 命名推荐两种方式：“MyName” or “my_name”

五、字符编码

1.指定字符集

#!/usr/bin/env python #指定解释器
# -*- coding: utf-8 -*- #指定字符集
 
print "你好，世界"

2.设置模版

[Settings] --> [Editor] --> [File and Code Templates] --> [Python Script]

3.注释

单行注释：# 被注释内容
多行注释：""" 被注释内容 """ （三个引号，单引号双引号均可。）

六、变量

1.声明变量

name = "Will"

上述代码声明了一个变量，变量名为： name，变量name的值为："Will"

2.变量定义的规则

• 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']

3.变量的赋值

name = "Will Wang"
name2 = name #name2指向name所指向的"Will Wang"
print(name, name2) 
 
name = "Jack"  #内存中开辟新地址保存为“Jack”
print(name, name2)
print("What is the value of name2 now?\n" + name2)

七、用户输入

1. 输入用户名

• 2.x

name = raw_input("Please input your name:")
print("Welcome," + name)

• 3.x

name = input("Please input your name:")
print("Welcome," + name)

2. 格式化字符串

name = input("Please input your name:")
age = int(input("Please input your age:")) #convert str to int
job = input("Please input your job:")
 
msg = '''
Information of user %s:
Name:   %s
Age :   %d
Job :   %s
'''%(name, name, age, job)
print(msg)

Ctrl + D 复制当前行
占位符：%s = string 字符，%d = digital 数字，%f = 小数、浮点
input 默认输入的是字符串，数字需要用int()转换

3. 常用模块初识

• getpass 输入密码

#Pycharm下不可用，仅限于Linux命令行或Windows的CMD
import getpass
username = input("username:")
password = getpass.getpass("password:")
print(username, password)

• OS 调用系统命令

#!/usr/bin/env python
# -*- coding: utf-8 -*-
 
import os
 
os.system("df -h")  #调用系统命令

import os

os.system("df")
os.mkdir("yourDir")
cmd_res = os.popen("df -h").read() #读取内存中的显示值并打印

4. 自己写个模块

python tab补全模块

• for Mac

import sys
import readline
import rlcompleter
 
if sys.platform == 'darwin' and sys.version_info[0] == 2:
    readline.parse_and_bind("bind ^I rl_complete")
else:
    readline.parse_and_bind("tab: complete")  # linux and python3 on mac
 
for mac

• for Linux

#!/usr/bin/env python
# python startup file
import sys
import readline
import rlcompleter
import atexit
import os
# tab completion
readline.parse_and_bind('tab: complete')
# history file 
histfile = os.path.join(os.environ['HOME'], '.pythonhistory')
try:
    readline.read_history_file(histfile)
except IOError:
    pass
atexit.register(readline.write_history_file, histfile)
del os, histfile, readline, rlcompleter
 
for Linux

自己写的tab.py模块只能在当前目录下导入，如果想在系统的任何一个地方都使用，要把这个tab.py放到python全局环境变量目录里。
一般都放在一个叫Python/2.7/site-packages目录下。
这个目录在不同的OS里放的位置不一样，用print(sys.path)可以查看python环境变量列表。

八、表达式if...else

1. 用户登录验证

• 判断用户名和密码

user = "will"
passwd = "wang1234"
username = input("username:")
password = input("password:")
 
if user == username:
    print("Username is correct...")
    if passwd == password:
        print("Welcome back, %s" %username)
    else:
        print("Password is not invaild...")
else:
    print("Guess it again, %s" %username)

#优化v1
user = "will"
passwd = "wang1234"
username = input("username:")
password = input("password:")
 
if user == username and passwd == password: # 用and同时判断username和password
    print("Welcome back, %s" %username)
else:
    print("Invalid username or password...")

2. 猜年龄

age = 31
guess_num = int(input("Please input the number you guess:"))

if guess_num == age:
    print("Congratulations! You got it!")
elif guess_num > age:
    print("Think it smaller.")
else:
    print("Think it bigger.")

九、循环

1. for循环

• 最简单的循环10次

for i in range(10):
    print("loop:", i )

• 年龄游戏

age = 31
for i in range(10):
    guess_num = int(input("Please input the number you guess:"))
    if guess_num == age:
        print("Congratulations! You got it!")
        break #停止往后继续走，跳出整个loop
    elif guess_num > age:
        print("Think it smaller.")
    else:
        print("Think it bigger.")

• 年龄游戏（尝试3次）

age = 31
for i in range(10):
    if i < 3:
        guess_num = int(input("Please input the number you guess:"))
        if guess_num == age:
            print("Congratulations! You got it!")
            break #停止往后继续走，跳出整个loop
        elif guess_num > age:
            print("Think it smaller.")
        else:
            print("Think it bigger.")
    else:
        print("You have tried too many times, good bye.")
        break

• 年龄游戏（每尝试3次，询问是否继续）

age = 31
counter = 0 #自己的计数器
for i in range(10):
    if counter < 3:
        guess_num = int(input("Please input the number you guess:"))
        if guess_num == age:
            print("Congratulations! You got it!")
            break #停止往后继续走，跳出整个loop
        elif guess_num > age:
            print("Think it smaller.")
        else:
            print("Think it bigger.")
    else:
        continue_confirm = input("Do you want try it again? type y to continue : ")
        if continue_confirm == "y":
            counter = 0
            continue #跳出本次循环
        else:
            print("bye")
            break
    counter += 1

2. while循环

• 年龄游戏

age = 31

count = 0
while True:
    guess_num = int(input('Please input your guees number:'))
    if guess_num == age:
        print('Yes, you got it!')
        break
    elif guess_num < age:
        print('Please think it bigger!')
    else:
        print('Please think it smaller!')

• 年龄游戏（尝试3次）

age = 31

count = 0
while count < 3:
    guess_num = int(input('Please input your guess number:'))
    if guess_num == age:
        print('Yes, you got it!')
        break
    elif guess_num < age:
        print('Please think it bigger')
    else:
        print('Please think it smaller!')
    count += 1
else:
    print('You have trid too many times. Byebye')

• 年龄游戏（每尝试3次，询问是否继续）

age = 31

count = 0
while count < 3:
    guess_num = int(input('Please input your guess number:'))
    if guess_num == age:
        print('Yes, you got it!')
        break
    elif guess_num < age:
        print('Please think it bigger')
    else:
        print('Please think it smaller!')
    count += 1
    if count == 3:
        continue_confirm = input('Do you want keep tring?')
        if continue_confirm != 'n':         # !=是不等于
            count = 0

十、作业

作业一：博客

作业二：编写登陆接口

• 输入用户名密码
• 认证成功后显示欢迎信息
• 输错三次后锁定

作业三：多级菜单

• 三级菜单
• 可依次选择进入各子菜单
• 所需新知识点：列表、字典

1. 流程图：www.processon.com
2. Readme.md
3. test.md