#read
f = open('/Users/michael/test.txt', 'r')#无则IOError
pass
f.close()
#防止错误
with open('/path/to/file', 'r') as f:
    pass
f.read() #read all
f.read(int) #read for size
f.readline()#read by lines
f.readlines()# return to a list with all lines

#open
r:read
w:write#若文件存在则文件长度清为0若文件不存在则建立该文件
a:add#若文件不存在，则会建立该文件，如果文件存在，写入的数据会被加到文件尾
b:binary
+:read&write
'rb'#读取图片。视频等二进制文件

#write
#紧接着写，没有换行
#return the lenth of str

#StringIO
>>> from io import StringIO
f = StringIO('Hello!\nHi!\nGoodbye!')#默认值初始化
>>> f = StringIO()      #DEFINITION
>>> f.write('hello')    #WRITE
5
>>> f.write(' ')
1
>>> f.write('world!')
6
>>> print(f.getvalue()) #GET ALL STR
hello world!

#BytesIO
>>> from io import BytesIO
>>> f = BytesIO()
>>> f.write('中文'.encode('utf-8'))
6
>>> print(f.getvalue())
b'\xe4\xb8\xad\xe6\x96\x87

#os
import os
os.name#posix:Linux,Unix,Mac OS/nt:windows
os.environ#环境变量
os.environ.get('key')#get the path with name:key
os.path.abspath('.')#当前目录绝对路径
os.path.join(str,str)#join path
os.mkdir(path)#create one file
>>> os.path.split('/Users/michael/testdir/file.txt')
('/Users/michael/testdir', 'file.txt')
>>> os.path.splitext('/path/to/file.txt')
('/path/to/file', '.txt')
os.rename('test.txt', 'test.py')
os.remove('test.py')

>>> import pickle
>>> d = dict(name='Bob', age=20, score=88)
>>> f=open('dump.txt','wb')
#pickle.dumps(d),把任意对象序列化成一个bytes
>>> pickle.dump(d,f)#序列化对象并存入一个file-like object
>>> f.close()
>>> f=open('dump.txt','rb')
>>> d=pickle.load(f)    #反序列化
>>> f.close()
>>> d
{'score': 88, 'name': 'Bob', 'age': 20}

import ison
>>> d = dict(name='Bob', age=20, score=88)
>>> json.dumps(d)
'{"age": 20, "score": 88, "name": "Bob"}'
#json.dump()#write in file-like object
json.lodes()#反序列化
json.lode()#from file-like object 反序列化

#json序列化类