Python Note

 

1. install

• website: https://www.python.org/
• version: 2.7.1
• install: run the msi install package and do not forget to check the options of "pip" and "add python.exe to Path"
• path: C:\Python27
• exit() 
• excute python file  in Mac/Linux start with

#!/usr/bin/env python　

2. cons

• 解释性语言，运行慢
• 无法加密

3. basic

    a. input/output

name=raw_input("enter your name:")
print "hi",name

　 b. 缩进的语句视为代码块

    c. 大小写敏感

    d. 转义字符\ 标识字符串内部特殊字符

print "I\'m learning \nPython"
print r"I\'m learning \nPython"
print """line1
line2
line3
"""

　　

    e. 全部大写的变量名表示常量

    f. 编码 

       源码中包含中文的时候，保存用UTF-8 编码（可变长编码），文件头添加以下两行， 用于读取源码时使用UTF-8编码读取文本

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

print u"这".encode("utf-8")

　 g. 格式化

       %用来格式化字符串

print "hi, %s aged %d" %("day", 25)

　 h. list

       一个有序可变的列表

line1=["lily", 23, True]
team=["a","bcd",line1]
print len(team)

#access the element
print team[2][2]
print "the first element %s" %(team[0])
print  "last element %s and the second last element %s" %(team[-1],team[-2])

#add/insert element
team.append("ij")
team.insert(1,"someone")
print team

#delete element 
team.pop()
print team
team.pop(0)
print team

#replace element
team[2]="newone"

print team

#empty list
emptyteam=[]
print len(emptyteam)

　　不可变的列表tuple，初始化后不改变，无append/insert 等方法，代码更加安全

#tuple
row=("to","two",2)

#tuple with one element
row2=(1,)

print row[2]

　　i. 条件判断

birth=int(raw_input("birth:"))
if birth>2000:
	print "child of", birth
elif birth>1990:
	print "young of", birth
else:
	print "old", birth

   　j. 循环

#for 
sum=0
for x in range(101):
	sum=sum+x
print sum

#while 
sum=0
n=99
while n>0:
	n=n-2
	sum=sum+n
print sum

　  k. dictionary

　 key-value 存储方式

#dictionary
roster={'angel':10,'simon':20,'tony':30}
print roster['simon']

#delete key
roster.pop('tony')
print roster

#set which store key only
s=set([1,2,3])
s.add(4)
print s

s.remove(4)
print s