Introduction à la méthode de traitement de fichiers python-open

pythonFonction intégréeopen() est utilisée pour ouvrir des fichiers et créer des fichiersObjets

Syntaxe

open(name[,mode[,bufsize]])

name : nom du fichier

mode : spécifier le mode d'ouverture du fichier

r : lecture seule

w : écrire

a : ajouter

　r,w,a prend en charge les opérations d'entrée et de sortie en même temps

　rb,wb ouvert en mode binaire

bufsize : définir la sortiecache

　0 Indique l'absence de tampon de sortie

 ; 1 indique l'utilisation du tampon

 ; Un nombre négatif indique l'utilisation des paramètres par défaut du système

 ; la taille spécifiée

#以只读方式打开text.txt文件，赋值给f1变量
>>> f1 = open('test.txt','r')

#查看f1数据类型
>>> type(f1)
<class &#39;_io.TextIOWrapper&#39;>

#读取文件内容，以字符串形式返回
>>> f1.read()
&#39;h1\nh2\nh3\nh4\nh5\nh6&#39;

#此时指针处于文件末尾，通过tell获取当前指针位置，通过seek重新指定指针位置
>>> f1.readline()
&#39;&#39;
>>> f1.tell()

>>> f1.seek(0)

#单行读取
>>> f1.readline()
&#39;h1\n&#39;

#读取余下所有行，以列表方式返回
>>> f1.readlines()
[&#39;h2\n&#39;, &#39;h3\n&#39;, &#39;h4\n&#39;, &#39;h5\n&#39;, &#39;h6&#39;]

#文件名
>>> f1.name
&#39;test.txt&#39;

#关闭文件
>>> f1.close()

#文件写入
f2 = open(&#39;test.txt&#39;,&#39;w+&#39;)
f2.write(&#39;hello&#39;)
f2.close()

#向文件追加内容
f3 = open(&#39;test.txt&#39;,&#39;a&#39;)
f3.write(&#39;hello&#39;)
f3.close()

#通过flush，将缓冲区内容写入文件
#write将字符串值写入文件
f3 = open(&#39;test.txt&#39;,&#39;w+&#39;)
for line in (i**2 for i in range(1,11)):
    f3.write(str(line)+&#39;\n&#39;)
f3.flush()
#f3.close()

#writelines将列表值写入文件
f3 = open(&#39;test.txt&#39;,&#39;w+&#39;)
lines = [&#39;11&#39;,&#39;22&#39;,&#39;33&#39;,&#39;44&#39;]
f3.writelines(lines)
f3.seek(0)
print(f3.readlines())
f3.close()
#执行结果：[&#39;11223344&#39;]

>>> f3.closed
True
>>> f3.mode
&#39;w+&#39;
>>> f3.encoding
&#39;cp936&#39;

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 will 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 are handled. It can be None, '', |  '\n', '\r', and '\r\n'.  It works as follows: |  
 |  * On input, if newline is None, universal newlines mode is
 |    enabled. Lines in the input can end in '\n', '\r', or '\r\n', and
 |    these are translated into '\n' before being returned to the |    caller. If it is '', universal newline mode is enabled, but line |    endings are returned to the caller untranslated. If it has any of |    the other legal values, input lines are only terminated by the given |    string, and the line ending is returned to the caller untranslated. |  
 |  * On output, if newline is None, any '\n' characters written are |    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 are translated |    to the given string. |  
 |  If line_buffering is True, a call to flush is 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 no effect if the file is already closed. |  
 |  detach(self, /) |      Separate the underlying buffer from the TextIOBase and return it. |      
 |      After the underlying buffer has 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 use a file descriptor. |  
 |  flush(self, /) |      Flush write buffers, if applicable. |      
 |      This is not implemented for read-only and non-blocking streams. |  
 |  isatty(self, /) |      Return whether this is an 'interactive' stream. |      
 |      Return False if it can't be determined.
 |  
 |  read(self, size=-1, /) |      Read at most n characters from stream. |      
 |      Read from underlying buffer until we have n characters or we hit EOF. |      If n is negative or omitted, read until EOF. |  
 |  readable(self, /) |      Return whether object was opened for reading. |      
 |      If False, read() will raise OSError. |  
 |  readline(self, size=-1, /) |      Read until newline or EOF. |      
 |      Returns an empty string if EOF is 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 are: |      
 |      * 0 -- start of stream (the default); offset should be zero or positive |      * 1 -- current stream position; offset may be 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() will raise OSError. |      This method may need to do a test seek(). |  
 |  tell(self, /) |      Return current stream position. |  
 |  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. |  
 |  writable(self, /) |      Return whether object was opened for writing. |      
 |      If False, write() will 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 be specified to control the number of lines read: no more |      lines will 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

Afin d'éviter d'oublier de fermer le fichier après l'avoir ouvert, vous pouvez gérer le contexte Lorsque le bloc de code with est exécuté, les ressources du fichier seront automatiquement fermées en interne et libérées.

with open("test.txt","a+") as f:
    f.write("hello world!")

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