19-python_文件和目录

淩亂°似流年 2022-09-17 07:24 166阅读 0赞

I/O 操作  
\- 文件的打开和创建  
\- 文件读取  
\- 文件写入  
\- 内容查找和替换  
\- 文件 删除 复制 重命名  
\- 目录操作

# 1. 文件读写 #

\- open()  
\- file()  
\- file.read()  
\- file.write()  
\- file.close()  
  
1.1 open  
\- file\_handler = open( filename\[, mode\[, buffer\]\])  
  
>>> help( open )  
Help on built-in function open in module \_\_builtin\_\_:  
  
open(...)  
open(name\[, mode\[, buffering\]\]) -> file object  
  
Open a file using the file() type, returns a file object. This is the  
preferred way to open a file. See file.\_\_doc\_\_ for further information.  
  
1.1.1 filename  
\- 相对路径的文件  
\- 局的路径的文件  
\- window下, 路径分隔符"\\\\" 或 "/"  
  
1.1.2 mode  
\- r 只读(默认)  
\- r+ 读写, 先读后写-追加, 先写-从头开始覆盖  
\- w 写入, 清空, 没有则创建  
\- w+ 写入, 清空, 没有则创建(可写入输出)  
\- a 写入, 追加, 没有则创建  
\- a+ 读写, 追加, 没有则创建  
\- b 打开二级制的文件, 可与 r w a + 结合使用  
\- U 支持所有的换行符, \\r \\n \\r\\n  
  
1.2 read -----file.read()  
>>> help(file.read)  
Help on method\_descriptor:  
  
read(...)  
read(\[size\]) -> read at most size bytes, returned as a string.  
  
If the size argument is negative or omitted, read until EOF is reached.  
Notice that when in non-blocking mode, less data than what was requested  
may be returned, even if no size parameter was given.  
  
E:\\desktop\\python\\py\_src>type a.txt  
hello!  
I'm Forward.  
E:\\desktop\\python\\py\_src>python  
  
\#\#\#\#\#\#\#\#\# file() \#\#\#\#\#\#\#\#\#\#\#\#\#\#\#  
>>> file\_handler = open("a.txt")  
>>> file\_handler  
<open file 'a.txt', mode 'r' at 0x012D6230>  
>>> content = file\_handler.read()  
>>> content  
"hello!\\nI'm Forward.\\n"  
>>> print content  
hello!  
I'm Forward.  
  
>>> file\_handler.close()  
>>> file\_handler  
<closed file 'a.txt', mode 'r' at 0x012D6230>  
>>> file\_handler.read()  
Traceback (most recent call last):  
File "<stdin>", line 1, in <module>  
ValueError: I/O operation on closed file  
  
\#\#\#\#\#\#\#\#\# file() \#\#\#\#\#\#\#\#\#\#\#\#\#\#\#  
>>> file\_handler = file( "E:/desktop/python/py\_src/a.txt" )  
>>> file\_handler  
<open file 'E:/desktop/python/py\_src/a.txt', mode 'r' at 0x012E6230>  
>>> file\_handler.read()  
"hello!\\nI'm Forward.\\n"  
>>> file\_handler.close()  
  
1.3 close ---- file.close()  
  
>>> help( file.close )  
Help on method\_descriptor:  
  
close(...)  
close() -> None or (perhaps) an integer. Close the file.  
  
Sets data attribute .closed to True. A closed file cannot be used for  
further I/O operations. close() may be called more than once without  
error. Some kinds of file objects (for example, opened by popen())  
may return an exit status upon closing.  
  
1.4 write ---- file.write()  
  
>>> help( file.write )  
Help on method\_descriptor:  
  
write(...)  
write(str) -> None. Write string str to file.  
  
Note that due to buffering, flush() or close() may be needed before  
the file on disk reflects the data written.  
  
>>> newfile = open("a.txt", "w")  
>>> newfile.write( "hello, I'm a new file!" )  
>>> newfile.flush()  
>>> newfile.close()  
>>> newfile = file( "a.txt" )  
>>> newfile.read()  
"hello, I'm a new file!"  
>>> newfile.close()

# 2. 文件对象方法 #

\- fileObject.close()  
\- string = fileObject.readline(\[size\])  
\- list = fileObject.readlines(\[size\])  
\- contentString = fileObject.read(\[size\])  
\- fileObject.next()  
\- fileObject.write(string)  
\- fileObject.writelines(list)  
\- fileObject.seek(offset, options)  
\- fileObject.flush()  
  
2.1 read(\[size\]) - string  
\- read(size) 每次读size个字节  
\- read() 一次读取所有内容  
  
2.2 readline(\[size\]) - string  
\- readline(size) 每次读一行中多少个字  
\- readline 每次读一行, 读到行末  
  
>>> help(file.readline)  
Help on method\_descriptor:  
  
readline(...)  
readline(\[size\]) -> next line from the file, as a string.  
  
Retain newline. A non-negative size argument limits the maximum  
number of bytes to return (an incomplete line may be returned then).  
Return an empty string at EOF.  
  
>>> afile = open("a.txt")  
>>> afile.readline()  
'\\n'  
>>> afile.readline()  
'hello\\n'  
>>> afile.readline()  
"I'm Forwar.\\n"  
>>> afile.readline()  
"What's your name?\\n"  
>>> afile.readline()  
'Bye!\\n'  
>>> afile.readline()  
''  
>>> afile.close()  
  
2.3 readlines(\[size\])  
  
>>> help(file.readlines)  
Help on method\_descriptor:  
  
readlines(...)  
readlines(\[size\]) -> list of strings, each a line from the file.  
  
Call readline() repeatedly and return a list of the lines so read.  
The optional size argument, if given, is an approximate bound on the  
total number of bytes in the lines returned.  
  
>>> afile = open("a.txt")  
>>> afile.readlines()  
\['\\n', 'hello\\n', "I'm Forwar.\\n", "What's your name?\\n", 'Bye!\\n'\]  
>>> afile.close()  
  
2.4 next()  
\- 读完, 会停止迭代, 不会像read...() 方法读完后返回空串  
  
>>> help( file.next )  
Help on wrapper\_descriptor:  
  
next(...)  
x.next() -> the next value, or raise StopIteration  
  
>>> afile = open("a.txt")  
>>> afile.next()  
'\\n'  
>>> afile.next()  
'hello\\n'  
>>> afile.next()  
"I'm Forwar.\\n"  
>>> afile.next()  
"What's your name?\\n"  
>>> afile.next()  
'Bye!\\n'  
>>> afile.next()  
Traceback (most recent call last):  
File "<stdin>", line 1, in <module>  
StopIteration  
>>> afile.next()  
Traceback (most recent call last):  
File "<stdin>", line 1, in <module>  
StopIteration  
>>> afile.close()  
  
2.5 writelines(list)  
>>> afile = open("a.txt")  
>>> afile.close()  
>>> afile = open("a.txt", "a")  
>>> appendList = \["one\\n", "two\\n"\]  
>>> afile.writelines(appendList)  
>>> afile.close()  
  
2.6 seek(offset, whence) 移动文件指针  
\- whence = 0 文件开始  
\- whence = 1 当前位置  
\- whence = 2 文件末尾  
>>> help(file.seek)  
Help on method\_descriptor:  
  
seek(...)  
seek(offset\[, whence\]) -> None. Move to new file position.  
  
Argument offset is a byte count. Optional argument whence defaults to  
0 (offset from start of file, offset should be >= 0); other values are 1  
(move relative to current position, positive or negative), and 2 (move  
relative to end of file, usually negative, although many platforms allow  
seeking beyond the end of a file). If the file is opened in text mode,  
only offsets returned by tell() are legal. Use of other offsets causes  
undefined behavior.  
Note that not all file objects are seekable.  
  
>>> afile = open("a.txt")  
>>> afile.read()  
"\\nhello\\nI'm Forwar.\\nWhat's your name?\\nBye!\\none\\ntwo\\n"  
>>> afile.read()  
''  
>>> afile.seek(0)  
>>> afile.read()  
"\\nhello\\nI'm Forwar.\\nWhat's your name?\\nBye!\\none\\ntwo\\n"  
>>> afile.close()