study note2

1continue：跳出本次循环，进入到下次循环

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# __author__ = "Deakin"
# Email: 469792427@qq.com
# Date: 2017/12/25

for i in range(0,10):
    if i<5:
        print("loop",i)
    else:
        continue
        print("hehe")
因此此程序并不会打印hehe


break：结束当前循环，并不是整个循环

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# __author__ = "Deakin"
# Email: 469792427@qq.com
# Date: 2017/12/25

for i in range(0,10):
    print("---------------",i)
    for j in range(0,10):
        print(j)
        if j>5:  #关于大于5，为什么还是会打印出6的问题 尚需研究
            break

打印结果：

--------------- 1
0
1
2
3
4
5
6

......

--------------- 9
0
1
2
3
4
5
6

2文件操作：
文件模式： 
1. r：只读模式，默认就是只读模式，读过一遍之后，指针就停留在原地 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# __author__ = "Deakin"
# Email: 469792427@qq.com
# Date: 2017/12/25

f=open("yesterday",'r',encoding="utf-8") #文件句柄
data=f.read()
print("----read----\n",data)

2. w：只写模式，它是创建一个空文件，会覆盖原文件，如果有同名原文件那么之前的内容就没有了

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# __author__ = "Deakin"
# Email: 469792427@qq.com
# Date: 2017/12/25

f=open("yesterday2",'w',encoding="utf-8") #新建了yesterday2文件，如果已有同名文件则会覆盖成空文件
f.write('-----write------\n'"those were such happy time and not so long ago, how I wonder where they gone")
date = f.read()
print(data)

Traceback (most recent call last):
File "C:/Users/Deakin/PycharmProjects/untitled2/12.15/write.py", line 9, in <module>
date = f.read()
io.UnsupportedOperation: not readable  #可以看到报错，写的模式下就不可读

3. a: 追加（不可读）：不覆盖原文件

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# __author__ = "Deakin"
# Email: 469792427@qq.com
# Date: 2017/12/25

f=open("yesterday",'a',encoding="utf-8") #a=append 追加
f.write("\nBut thay back again,just like a long lost friend, all the songs I love so well")
data=f.read()
print(data)

C:\Users\Deakin\PycharmProjects\untitled2\venv\Scripts\python.exe C:/Users/Deakin/PycharmProjects/untitled2/12.15/attend.py
Traceback (most recent call last):
File "C:/Users/Deakin/PycharmProjects/untitled2/12.15/attend.py", line 9, in <module>
data=f.read()
io.UnsupportedOperation: not readable   #依然不可读，但是打开yesterday文件发现句子已经追加进去了