About Python-open File Processing method Introduction

Python built-in function open () for opening files and creating file objects

Grammar

Open (Name[,mode[,bufsize]])

Name: File name

Mode: Specifies the open mode of the file

R: Read-only

W: Write

A: Additional

R+,w+,a+ supports both input and output operations

rb,wb+ opens in binary mode

BufSize: Defining output caching

0 indicates no output cache

1 indicates the use of buffering

Negative numbers mean using system default settings

A positive number indicates a buffer with an approximate specified size

#以只读方式打开text. txt file, assign to f1 variable >>> f1 = open (' Test.txt ', ' R ') #查看f1数据类型 >>> type (F1) <class ' _io. Textiowrapper ' > #读取文件内容, returns the >>> f1.read () ' H1\nh2\nh3\nh4\nh5\nh6 ' #此时指针处于文件末尾 as a string, using tell to get the current pointer position, Reassign pointer position by seek >>> f1.readline () ' >>> F1.tell () >>> f1.seek (0) #单行读取 >>> F1.readline () ' h1\n ' #读取余下所有行, returned as a list >>> f1.readlines () [' h2\n ', ' h3\n ', ' h4\n ', ' h5\n ', ' h6 '] #文件名 >> > f1.name ' test.txt ' #关闭文件 >>> f1.close () #文件写入f2 = open (' Test.txt ', ' w+ ') f2.write (' Hello ') f2.close () # Append content to File F3 = Open (' Test.txt ', ' a ') f3.write (' Hello ') f3.close () #通过flush, writes the buffer contents to the file #write writes the string value to the file F3 = Open (' Test.txt ', ' w+ ') for line in (i**2 for I in range (1,11)): F3.write (str (line) + ' \ n ') F3.flush () #f3. Close () #writelines将列表值写入文件f3 = Open (' Test.txt ', ' w+ ') lines = [' One ', ' a ', ' ', ', ']f3.writelines ' (lines) f3.seek (0) print (f3.readlines ()) F3.close () # Execution result: [' 11223344 ']>>> f3.closedtrue>>> f3.mode ' w+ ' >>> f3.encoding ' cp936 '

Help on Textiowrapper object:class textiowrapper (_textiobase) | Character and line based layer over a Bufferediobase object, buffer.   |  |  Encoding gives the name of the encoding that the stream would be | decoded or encoded with. It defaults to Locale.getpreferredencoding (False).   |  |  Errors determines the strictness of encoding and decoding (see | Help (codecs.  CODEC) or the documentation for Codecs.register) and | Defaults to "strict".   |  | NewLine controls how line endings is handled.  It can be None, ', |  ' \ n ', ' \ R ', and ' \ r \ n '.   It works as follows: |  |    * on input, if newline are None, universal newlines mode is | Enabled.    Lines in the input can end in ' \ n ', ' \ R ', or ' \ r \ n ', and |    These is translated into ' \ n ' before being returned to the | Caller.    If it is ", universal newline mode is enabled, but line | Endings is returned to the caller untranslated.    If it has any of |    The other legal values, input lines is terminated by the given | StringAnd the line ending are returned to the caller untranslated.   |  |    * On output, if newline was None, any ' \ n ' characters written is | Translated to the system default line separator, Os.linesep.    If | NewLine is ' or ' \ n ', no translation takes place.    If NewLine is any |    Of the other legal values, any ' \ n ' characters written is translated | to the given string.   |  |  If line_buffering is True, a call to flush was implied when a call to | Write contains a newline character.   |  |      Method Resolution Order: |      Textiowrapper |      _textiobase |      _iobase |   Builtins.object |  |   Methods defined here: |  |   GetState (...) |  |      init (self,/, *args, **kwargs) |  Initialize self. See Help (Type Self) for accurate signature.   |  |      New (*args, **kwargs) from Builtins.type |  Create and return a new object. See Help (type) for accurate signature.   |  |      Next (self,/) | Implement Next (self).   |  |      Repr (self,/) | Return repr (self).   |  | Close (self, /) | Flush and close the IO object.       |      | This method has a effect if the file is already closed.   |  |      Detach (self,/) | Separate the underlying buffer from the textiobase and return it.       |      |      After the underlying buffer have been detached, the textio is in an | unusable state.   |  |      Fileno (self,/) | Returns underlying file descriptor if one exists.       |      | OSError is raised if the IO object does not a file descriptor.   |  |      Flush (self,/) | Flush write buffers, if applicable.       |      | This isn't implemented for read-only and non-blocking streams.   |  |      Isatty (self,/) | Return whether this was an ' interactive ' stream.       |      | Return False If it can ' t be determined.   |  |      Read (self, size=-1,/) | Read at the most n characters from stream.       |      | Read from underlying buffer until we had n characters or we hit EOF.      | If n is negative or omitted, read until EOF.   |  |      Readable (self,/) | REturn whether object is opened for reading.       |      | If False, read () would raise OSError.   |  |      ReadLine (self, size=-1,/) | Read until newline or EOF.       |      | Returns an empty string if EOF are hit immediately.   |  |      Seek (self, cookie, whence=0,/) | Change stream position.       |      | Change the stream position to the given byte offset.      The offset is |  Interpreted relative to the position indicated by whence.      Values |       For whence is: |      | * 0--start of stream (the default);      Offset should be zero or positive | * 1--current stream position;      Offset May negative | * 2--end of stream;       Offset is usually negative |      | Return the new absolute position.   |  |      Seekable (self,/) | Return whether object supports random access.       |      | If False, Seek (), tell () and truncate () would raise OSError.      | This method is need to do a test seek ().   |  |      Tell (self,/) | Return current stream position.   | |  Truncate (self, pos=none,/) | Truncate file to size bytes.       |      |  File pointer is the left unchanged.      Size defaults to the current IO |  Position as reported by Tell (). Returns the new size.   |  |      Writable (self,/) | Return whether object is opened for writing.       |      | If False, write () would raise OSError.   |  |      Write (self, text,/) | Write string to stream.      |      Returns the number of characters written (which is always equal to | The length of the string).   |  |  ---------------------------------------------------------------------- |   Data descriptors defined here: |  |   Buffer |  |   Closed |  |      encoding | Encoding of the text stream.       |      | Subclasses should override.   |  |      Errors | The error setting of the decoder or encoder.       |      | Subclasses should override.   |  |   line_buffering |  |   name |  |      newlines | Line endings translated so far.       |      | Only line endings translated during reading ARE considered.       |      | Subclasses should override.   |  |  ---------------------------------------------------------------------- |   Methods inherited from _iobase: |  |   Del (...) |  |   Enter (...) |  |   Exit (...) |  |      ITER (self,/) | Implement iter (self).   |  |      ReadLines (self, hint=-1,/) | Return a list of lines from the stream.       |      |      Hint can specified to control the number of lines Read:no more |      Lines would be read if the total size (in bytes/characters) of all | Lines so far exceeds hint.   |  |   Writelines (self, lines,/) |  |  ---------------------------------------------------------------------- |   Data descriptors inherited from _iobase: |  | Dict

*with

To avoid forgetting to close after opening a file, you can manage the context and automatically close and release the file resource when the with code block finishes executing.

With open ("Test.txt", "A +") as F:    f.write ("Hello world!")