2.使用with子句，打开后文件会自动关闭，建议使用，并可以同时打开多个文件
with open('../config/file1.txt','r',encoding='utf-8') as fd1,\
open('../config/file2.txt','r',encoding='utf-8') as fd2:
print("I had open two files")
打开文件的8种模式
========= ===============================================================
Character Meaning
--------- ---------------------------------------------------------------
'r' open for reading (default)
'w' open for writing, truncating the file first
'x' create a new file and open it for writing
'a' open for writing, appending to the end of the file if it exists
'b' binary mode
't' text mode (default)
'+' open a disk file for updating (reading and writing)
'U' universal newline mode (deprecated)
========= ===============================================================
1.’r'，默认模式，参数可以不写，打开只读文件，写入报错
>>> fd = open('../config/file1.txt','r',encoding='utf-8')
>>> fd.write('java c rubby')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
io.UnsupportedOperation: not writable
2.‘w’，先truncate原文件，后写入，不可读，文件不存在则创建
>>> fd = open('../config/file1.txt','w',encoding='utf-8')
>>> print(fd.read())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
io.UnsupportedOperation: not readable
>>> fd.write('java rubby go')
>>> fd.close()
>>> fd = open('../config/file1.txt','r',encoding='utf-8')
>>> fd.read()
'java rubby go'
3.'x'，创建新文件，打开并写入，如果文件已经存在，则报错
>>> fd = open('../config/file21.txt','x',encoding='utf-8' )
>>> fd.read()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
io.UnsupportedOperation: not readable
>>> fd.write('123456')
>>> fd.close()
>>> fd = open('../config/file21.txt','r',encoding='utf-8')
>>> fd.read()
'123456'
>>> fd.close()
>>> fd = open('../config/file21.txt','x',encoding='utf-8')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
FileExistsError: [Errno 17] File exists: '../config/file21.txt'
4.’a'，追加写内容到文件末尾
>>> fd = open('../config/file1.txt','a',encoding='utf-8')
>>> fd.write('linux windows aix')
>>> fd.close()
>>> fd = open('../config/file1.txt','r',encoding='utf-8')
>>> fd.read()
'java rubby golinux windows aix'
5.'b'，二进制模式，比如流文件mp3，并且需要同时指定一种读写模式
>>> fd = open('/tmp/Front_Right.wav','b')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: Must have exactly one of create/read/write/append mode and at most one plus
>>> fd = open('/tmp/Front_Right.wav','rb')
>>> fd1 = open('/tmp/Front_Right.wav','wb')
>>> fd2 = open('/tmp/Front_Right.wav','ab')
>>> fd2 = open('/tmp/Front_Right.wav','w+b')
>>> fd2 = open('/tmp/Front_Right.wav','r+b')
6.'t'，文本模式，默认打开文本并读取模式rt
7.'+'，打开硬盘文件读写
r+，打开并写入
>>> fd = open('../config/file1.txt','r+',encoding='utf-8')
>>> fd.read()
'java rubby golinux windows aix'
>>> fd.write("mage")
>>> fd.seek(0)
>>> fd.read()
'java rubby golinux windows aixmage'
w+，打开文件读写，文件存在则覆盖，不存在则创建
>>> fd = open('../config/file4.txt','w+',encoding='utf-8')
>>> fd.write('guangzhou')
>>> fd.seek(0)
>>> fd.read()
'guangzhou'
>>> fd.seek(0)
>>> fd.write('hangzhou')
>>> fd.seek(0)
>>> fd.read()
'hangzhouu'
a+，打开文件读写，存在则将指针置于末尾，不存在则创建新文件
>>> fd = open('../config/file4.txt','a+',encoding='utf-8')
>>> fd.read()
>>> fd.seek(0)
>>> fd.read()
'hangzhouu'
>>> fd.close()
>>> fd = open('../config/file4.txt','a+',encoding='utf-8')
>>> fd.write('beijing')
>>> fd.read()
>>> fd.seek(0)
>>> fd.read()
'hangzhouubeijing'
rb+, wb+, ab+ 对象是二进制，其他以上面一样
8.‘U’，deprecated
1.f.tell()，告知字符指针位置
2.f.seek()，移动字符指针位置，f.seek(0)文件开头
>>> fd = open('../config/file4.txt','r',encoding='utf-8')
>>> fd.tell()
>>> fd.seek(0)
>>> fd.tell()
>>> fd.read(1)
'h'
>>> fd.tell()
>>> fd.read(2)
'an'
>>> fd.tell()
>>> fd.seek(0)
>>> fd.readline()
'hangzhouubeijing\n'
>>> fd.tell()
读取文件的4个read，默认从头开始读，并将将指针留在行尾
1.fd.read(size)
默认省略size，size为整型，字符个数
读取全部内容到内存，并将指针留在行尾
大文件读取不要用，占内存
返回的是字符串类型
>>> fd = open('../config/file4.txt','r',encoding='utf-8')
>>> fd.read()
'hangzhouubeijing'
>>> fd.seek(0)
>>> fd.read(1)
'h'
>>> fd.read(2)
'an'
>>> fd.read(3)
'gzh'
>>> fd.seek(0)
>>> fd.read(6)
'hangzh'
2.fd.readline(size)
默认一行行读取，size与上面一样
占用内存小
每行结尾带换行符
>>> fd = open('../config/file4.txt','r',encoding='utf-8')
>>> fd.readline()
'hangzhouubeijing\n'
>>> fd.readline()
'shenzhen\n'
>>> fd.readline()
'shanghai\n'
>>> fd.readline(1)
'a'
>>> fd.readline(2)
'nh'
>>> fd.readline()
'ui\n'
>>> fd.readline()
'guangdong\n'
>>> fd.readline()
'zhejiang'
>>> fd.readline()
3.fd.readlines(size)
讲文本全部转换成列表，size表示下标
>>> fd = open('../config/file4.txt','r',encoding='utf-8')
>>> fd.readlines()
['hangzhouubeijing\n', 'shenzhen\n', 'shanghai\n', 'anhui\n', 'guangdong\n', 'zhejiang']
>>> fd.seek(0)
>>> fd.readlines(1)
['hangzhouubeijing\n']
>>> fd.readlines()
['shenzhen\n', 'shanghai\n', 'anhui\n', 'guangdong\n', 'zhejiang']
4.fd.readable()
返回布尔值，判断文件是否可读
>>> fd = open('../config/file4.txt','r',encoding='utf-8')
>>> fd.readable()
循环遍历迭代文本内容对象（遍历操作都可以这么干）
>>> fd = open('../config/file4.txt','r',encoding='utf-8')
>>> for line in fd:
... print(line)
hangzhouubeijing
shenzhen
shanghai
anhui
guangdong
zhejiang
>>> fd.seek(0)
>>> for index,line in enumerate(fd.readlines()):
... print(index,line)
0 hangzhouubeijing
1 shenzhen
2 shanghai
3 anhui
4 guangdong
5 zhejiang
close(self, /) 关闭打开的文件
| Flush and close the IO object.
| This method has no effect if the file is already closed.
detach(self, /) 干嘛用？
| Separate the underlying buffer from the TextIOBase and return it.
| After the underlying buffer has been detached, the TextIO is in an
| unusable state.
>>> fd.detach()
<_io.BufferedReader name='../config/file4.txt'>
>>> fd.read()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: underlying buffer has been detached
fileno(self, /) 返回文件描述符，干嘛用？
| Returns underlying file descriptor if one exists.
| OSError is raised if the IO object does not use a file descriptor.
>>> fd = open('../config/file4.txt','r',encoding='utf-8')
>>> fd.fileno()
>>> fd = open('../config/filexxx.txt','w+',encoding='utf-8')
>>> fd.fileno()
flush(self, /) 将缓存立即写入硬盘，提高效率
| Flush write buffers, if applicable.
| This is not implemented for read-only and non-blocking streams.
import time
import sys
for i in range(40):
sys.stdout.write("#")
sys.stdout.flush()
time.sleep(0.1)
isatty(self, /) 是否连接到终端设备
| Return whether this is an 'interactive' stream.
| Return False if it can't be determined.
seekable(self, /)
| Return whether object supports random access.
| If False, seek(), tell() and truncate() will raise OSError.
| This method may need to do a test seek().
truncate(self, pos=None, /)
| Truncate file to size bytes.
| File pointer is left unchanged. Size defaults to the current IO
| position as reported by tell(). Returns the new size.
>>> fd = open('../config/file4.txt','r+',encoding='utf-8')
>>> fd.truncate()
writable(self, /) 判断文件是否以写模式打开
| Return whether object was opened for writing.
>>> fd = open('../config/file4.txt','r+',encoding='utf-8')
>>> fd.writable()
>>> fd = open('../config/file1.txt','r',encoding='utf-8')
>>> fd.writable()
False
修改文件的两种方式：
1.全部读入内存，修改完毕之后覆盖写入源文件
2.一行一行读取内存，修改完毕之后写入新文件，用新文件覆盖旧文件
练习一：实现sed替换功能
练习二：修改haproxy配置文件
