Day1 初识Python

（1）变量与赋值

name = "wanghuafeng"
age = 29
print(name, age)

a和b交换值

a = 3
b = 5
tmp = a
a = b
b = tmp
print(a, b)

变量要求：

a.显式
b.nums_of_words = 19
c.NumsOfWords = 19  #驼峰写法
d."-"在任何语言中都是减号，保留符号
e.数字不能开头，可以在中间和结尾
f.特殊字符不能有，！@￥%……&*（）
g.不能有空格、只能是下划线、数字和字母，关键字不能作为变量

（2）字符编码

ASCII码表（2**8=128个字符）

unicode：统一码、万国码

每一个字符最少用2个字节（16位）来存储，即2**16=65536

utf-8:是针对unicode的可变长度元编码。

它可以使用1~4个字节表示一个符号，根据不同的符号而变化字节长度。

（3）Pycharm修改文件模板

依次打开：File—>Settings—>Editor—>File and Code Templates—>Python Scripts

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author: WangHuafeng

（4）多行打印

#！/usr/bin/env python
# -*- coding: utf-8 -*-
# Author: wanghuafeng
name = input("input your name:")
age = int(input("input your age:"))
job = input("input your job:")
#print("name is:", name + "\nage is:", age + "\njob is:", job)
msg = """
Information of user %s:
-------------------------
Name: %s
Age : %d
Job : %s
---------End-------------
""" % (name, name, age, job)
print(msg)

%d:整数

%f:浮点数

%s:字符串

代码中的注释

#注释一行最多不超过80个字符

"""
多行注释,
不用每行注释
"""

'''
也可以采用这个注释
'''

（5）隐藏输入密码

#!/usr/bin/env python

# -*- coding: utf-8 -*-

# Author: WangHuafeng

import getpass

username = input("请输入用户名：")

password = input("请输入密码：")

print(username, password)

注意：Pycharm上输入密码时没有隐藏，Linux上可以隐藏。

（6）导入模块

#!/usr/bin/env python

# -*- coding: utf-8 -*-

# Author: WangHuafeng

import os

cmd_java = os.system("java -version")

print(cmd_java)

注意：导入模块或自己的python文件时不能加.py即：import Hello

（7）Linux上增加tab补全

新建文件tab.py

# 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

保存到/usr/lib/python2.7/dist-packages目录中

python命令行中输入：import tab

即可tab查看命令提示。

（8）if判断

#！/usr/bin/env python
# -*- coding: utf-8 -*-
# Author: wanghuafeng

user = 'wanghuafeng'
passwd = '123456'

username = input("input your name:")
password = input("input your password:")

if user == username and passwd == password:
    print("Welcome to login...")
else:
    print("用户名或密码错误...")

（9）猜年龄

#！/usr/bin/env python
# -*- coding: utf-8 -*-
# Author: wanghuafeng

age = 22
counter = 0
for i in range(10):
    print("counter is :", counter)
    if counter < 3:
        guess_num = int(input("input your guess num:  "))
        if guess_num == age:
            print("Congratulations! You got it.")
            break
        elif guess_num > age:
            print("Think smaller!")
        else:
            print("Think Big...")
    else:
        continue_confirm = input("Do you want to continue because you are stupid:")
        if continue_confirm == 'y':
            counter = 0
            continue
        else:
            print("Bye.")
            break
    counter += 1