Python_文件操作

文件操作

1、文件路径：  如 d: '文件名称‘.后缀

2、编码方式： utf-8  gbk ......

3、操作方式： 只读，只写，追加，读写，写读......

　以什么编码方式存储的文件，就以什么编码打开进行操作。

具体表现：

只读： r

绝对路径
f = open('e:\a1.py', mode='r', encoding='utf-8')
content = f.read()
print(content)
f.close()

相对路径

f = open('xxx', mode='r', encoding='utf-8')
content = f.read()
f.close()

注释：绝对路径打开，需要 open（‘文件在硬盘中的地址+后缀’，mode=‘r’，encoding=‘utf-8’），如果路径是 a1 这样简短的文件名，需要另外加一个 不影响正常读取而且分割区分 

           a 在python中的关键字。
            相对路径  只需要文件在同一个目录下，并且文件名称正确，通过正确的格式就能打开。

只读： rb            bytes类型   系统内部 传输 存储 使用。

f = open('e:\t1.py', mode='rb')
content = f.read()
print(content)
f.close()

不需要设定编码方式，‘rb’已经内部默认
读写： r+  只能先读后写，并且不能续写，只能完成一步读写，不能是读写读写读写。

f = open('e:\t2.py', mode='r+', encoding='utf-8')
content = f.read()
contents = f.write('a11')
print(content,contents)
f.close()

只写 ： ‘w’  没有此文件就会创建文件，已经有的，删除原文件，再写入新文件

f = open('e:\t2.py', mode='w', encoding='utf-8')
content = f.write('asdadas')
print(content)
f.close()

写读： w+ 写读   先全部删除，然后写入

f = open('e:\t2.py', mode='w+', encoding='utf-8')
f.write('a11')
f.seek(0)
print(f.read())
f.close()

x， 只写模式【不可读；不存在则创建，存在则报错】

f = open('e:\t6.py', mode='x', encoding='utf-8')
f.write('a11aa')
f.close()

a， 追加模式【可读；   不存在则创建；存在则只追加内容；】

f = open('e:\t2.py', mode='a', encoding='utf-8')
f.write('1qqw')
print(f)
f.close()

a+， 写读【可读，可写】

f = open('e:\t2.py', mode='a+', encoding='utf-8')
f.write('阳展')
print(f.read())
f.close()

 "b"表示以字节的方式操作

• rb  或 r+b
• wb 或 w+b
• xb 或 w+b
• ab 或 a+b

 注：以b方式打开时，读取到的内容是字节类型，写入时也需要提供字节类型

class file(object)
    def close(self): # real signature unknown; restored from __doc__
        关闭文件
        """
        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.
        """
 
    def fileno(self): # real signature unknown; restored from __doc__
        文件描述符  
         """
        fileno() -> integer "file descriptor".
         
        This is needed for lower-level file interfaces, such os.read().
        """
        return 0    
 
    def flush(self): # real signature unknown; restored from __doc__
        刷新文件内部缓冲区
        """ flush() -> None.  Flush the internal I/O buffer. """
        pass
 
 
    def isatty(self): # real signature unknown; restored from __doc__
        判断文件是否是同意tty设备
        """ isatty() -> true or false.  True if the file is connected to a tty device. """
        return False
 
 
    def next(self): # real signature unknown; restored from __doc__
        获取下一行数据，不存在，则报错
        """ x.next() -> the next value, or raise StopIteration """
        pass
 
    def read(self, size=None): # real signature unknown; restored from __doc__
        读取指定字节数据
        """
        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.
        """
        pass
 
    def readinto(self): # real signature unknown; restored from __doc__
        读取到缓冲区，不要用，将被遗弃
        """ readinto() -> Undocumented.  Don't use this; it may go away. """
        pass
 
    def readline(self, size=None): # real signature unknown; restored from __doc__
        仅读取一行数据
        """
        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.
        """
        pass
 
    def readlines(self, size=None): # real signature unknown; restored from __doc__
        读取所有数据，并根据换行保存值列表
        """
        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.
        """
        return []
 
    def seek(self, offset, whence=None): # real signature unknown; restored from __doc__
        指定文件中指针位置
        """
        seek(offset[, whence]) -> None.  Move to new file position.
         
        Argument offset is a byte count.  Optional argument whence defaults to
(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.
        """
        pass
 
    def tell(self): # real signature unknown; restored from __doc__
        获取当前指针位置
        """ tell() -> current file position, an integer (may be a long integer). """
        pass
 
    def truncate(self, size=None): # real signature unknown; restored from __doc__
        截断数据，仅保留指定之前数据
        """
        truncate([size]) -> None.  Truncate the file to at most size bytes.
         
        Size defaults to the current file position, as returned by tell().
        """
        pass
 
    def write(self, p_str): # real signature unknown; restored from __doc__
        写内容
        """
        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.
        """
        pass
 
    def writelines(self, sequence_of_strings): # real signature unknown; restored from __doc__
        将一个字符串列表写入文件
        """
        writelines(sequence_of_strings) -> None.  Write the strings to the file.
         
        Note that newlines are not added.  The sequence can be any iterable object
        producing strings. This is equivalent to calling write() for each string.
        """
        pass
 
    def xreadlines(self): # real signature unknown; restored from __doc__
        可用于逐行读取文件，非全部
        """
        xreadlines() -> returns self.
         
        For backward compatibility. File objects now include the performance
        optimizations previously implemented in the xreadlines module.
        """
        pass

2.x

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, '',
    '
', '
', and '
'.  It works as follows:
    
    * On input, if newline is None, universal newlines mode is
      enabled. Lines in the input can end in '
', '
', or '
', and
      these are translated into '
' 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 '
' characters written are
      translated to the system default line separator, os.linesep. If
      newline is '' or '
', no translation takes place. If newline is any
      of the other legal values, any '
' 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.
    """
    def close(self, *args, **kwargs): # real signature unknown
        关闭文件
        pass

    def fileno(self, *args, **kwargs): # real signature unknown
        文件描述符  
        pass

    def flush(self, *args, **kwargs): # real signature unknown
        刷新文件内部缓冲区
        pass

    def isatty(self, *args, **kwargs): # real signature unknown
        判断文件是否是同意tty设备
        pass

    def read(self, *args, **kwargs): # real signature unknown
        读取指定字节数据
        pass

    def readable(self, *args, **kwargs): # real signature unknown
        是否可读
        pass

    def readline(self, *args, **kwargs): # real signature unknown
        仅读取一行数据
        pass

    def seek(self, *args, **kwargs): # real signature unknown
        指定文件中指针位置
        pass

    def seekable(self, *args, **kwargs): # real signature unknown
        指针是否可操作
        pass

    def tell(self, *args, **kwargs): # real signature unknown
        获取指针位置
        pass

    def truncate(self, *args, **kwargs): # real signature unknown
        截断数据，仅保留指定之前数据
        pass

    def writable(self, *args, **kwargs): # real signature unknown
        是否可写
        pass

    def write(self, *args, **kwargs): # real signature unknown
        写内容
        pass

    def __getstate__(self, *args, **kwargs): # real signature unknown
        pass

    def __init__(self, *args, **kwargs): # real signature unknown
        pass

    @staticmethod # known case of __new__
    def __new__(*args, **kwargs): # real signature unknown
        """ Create and return a new object.  See help(type) for accurate signature. """
        pass

    def __next__(self, *args, **kwargs): # real signature unknown
        """ Implement next(self). """
        pass

    def __repr__(self, *args, **kwargs): # real signature unknown
        """ Return repr(self). """
        pass

    buffer = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    closed = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    encoding = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    errors = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    line_buffering = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    name = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    newlines = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    _CHUNK_SIZE = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    _finalizing = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

3.x

注意： 

yang123an
123456789
f = open('e:\t2.py', mode='r+', encoding='utf-8')
# content = f.read(2)  # read(N) 从头开始读取N个字符     ya
# print(content)
f.seek(2)  # 是按照字节定光标的位置开始
content = f.read(3)   #读取3个字符                               ng1
print(content)  
f.tell()   # 告诉你当前光标的位置
print(f.tell())
# content = f.read()
# print(content)
# f.tell()
# f.readable()  # 是否可读  返回True  or  False
# line = f.readline()  # 一行一行的读
# line = f.readlines()  # 每一行当成列表中的一个元素，添加到list中
# f.truncate(4)     #对原文件进行截取一段读取
# for line in f:
#     print(line)
# f.close()

为避免打开文件后忘记关闭，可以通过管理上下文，即：

with open（‘log’，‘r’）as f：

　　pass

如此方式，当with代码块执行完毕时，内部会自动关闭并释放文件资源。

在Python 2.7 及以后，with又支持同时对多个文件的上下文进行管理。