python内置函数4-file()
Help on> class file(object)|file(name[, mode[, buffering]]) -> file object
|
|Open a file.The mode can be 'r', 'w' or 'a' for reading (default),
|writing or appending.The file will be created if it doesn't exist
|when opened for writing or appending; it will be truncated when
|opened for writing.Add a 'b' to the mode for binary files.
|Add a '+' to the mode to allow simultaneous reading and writing.
|If the buffering argument is given, 0 means unbuffered, 1 means line
|buffered, and larger numbers specify the buffer> |to open a file is with the builtin open() function.
|Add a 'U' to mode to open the file for input with universal newline
|support.Any line ending in the input file will be seen as a '\n'
|in Python.Also, a file so opened gains the attribute 'newlines';
|the value for this attribute is one of None (no newline read yet),
|'\r', '\n', '\r\n' or a tuple containing all the newline types seen.
|
|'U' cannot be combined with 'w' or '+' mode.
|
|Methods defined here:
|
|__delattr__(...)
| x.__delattr__('name') <==> del x.name
|
|__enter__(...)
| __enter__() -> self.
|
|__exit__(...)
| __exit__(*excinfo) -> None.Closes the file.
|
|__getattribute__(...)
| x.__getattribute__('name') <==> x.name
|
|__init__(...)
| x.__init__(...) initializes x; see help(type(x)) for signature
|
|__iter__(...)
| x.__iter__() <==> iter(x)
|
|__repr__(...)
| x.__repr__() <==> repr(x)
|
|__setattr__(...)
| x.__setattr__('name', value) <==> x.name = value
|
|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.
|
|fileno(...)
| fileno() -> integer "file descriptor".
|
| This is needed for lower-level file interfaces, such os.read().
|
|flush(...)
| flush() -> None.Flush the internal I/O buffer.
|
|isatty(...)
| isatty() -> true or false.True if the file is connected to a tty device.
|
|next(...)
| x.next() -> the next value, or raise StopIteration
|
|read(...)
| read() -> read at most> |
| If the> | Notice that when in non-blocking mode, less data than what was requested
| may be returned, even if no> |
|readinto(...)
| readinto() -> Undocumented.Don't use this; it may go away.
|
|readline(...)
| readline() -> next line from the file, as a string.
|
| Retain newline.A non-negative> | number of bytes to return (an incomplete line may be returned then).
| Return an empty string at EOF.
|
|readlines(...)
| readlines() -> list of strings, each a line from the file.
|
| Call readline() repeatedly and return a list of the lines so read.
| The optional> | total number of bytes in the lines returned.
|
|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 end of file, usually negative,> | 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.
|
|tell(...)
| tell() -> current file position, an integer (may be a long integer).
|
|truncate(...)
| truncate() -> None.Truncate the file to at most> |
| Size defaults to the current file position, as returned by tell().
|
|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.
|
|writelines(...)
| 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.
|
|xreadlines(...)
| xreadlines() -> returns self.
|
| For backward compatibility. File objects now include the performance
| optimizations previously implemented in the xreadlines module.
|
|----------------------------------------------------------------------
|Data descriptors defined here:
|
|closed
| True if the file is closed
|
|encoding
| file encoding
|
|errors
| Unicode error handler
|
|mode
| file mode ('r', 'U', 'w', 'a', possibly with 'b' or '+' added)
|
|name
| file name
|
|newlines
| end-of-line convention used in this file
|
|softspace
| flag indicating that a space needs to be printed; used by print
|
|----------------------------------------------------------------------
|Data and other attributes defined here:
|
|__new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
file(name[, mode[, buffering]])
Constructor function for the file type, described further in section File Objects. The constructor’s arguments are the same as those of the open() built-in function described below.
When opening a file, it’s preferable to use open() instead of invoking this constructor directly. file is more suited to type testing (for example, writing isinstance(f, file)).
中文说明：
读出一个文件的内容。
file()函数是2.2中新增的函数，它与open()函数一样，相当于open()的别名，不过比open()更直观一些。
lines = file(filename).readlines()
for line in lines:
print line
序号方法及描述
1file.close()
关闭文件。关闭后文件不能再进行读写操作。
2file.flush()
刷新文件内部缓冲，直接把内部缓冲区的数据立刻写入文件, 而不是被动的等待输出缓冲区写入。
3file.fileno()
返回一个整型的文件描述符(file descriptor FD 整型), 可以用在如os模块的read方法等一些底层操作上。
4file.isatty()
如果文件连接到一个终端设备返回 True，否则返回 False。
5file.next()
返回文件下一行。
6file.read()
从文件读取指定的字节数，如果未给定或为负则读取所有。
7file.readline()
读取整行，包括 "\n" 字符。
8file.readlines()
读取所有行并返回列表，若给定sizeint>0，返回总和大约为sizeint字节的行, 实际读取值可能比sizhint较大, 因为需要填充缓冲区。
9file.seek(offset[, whence])
设置文件当前位置
10file.tell()
返回文件当前位置。
11file.truncate()
截取文件，截取的字节通过size指定，默认为当前文件位置。
12file.write(str)
将字符串写入文件，没有返回值。
13file.writelines(sequence)
向文件写入一个序列字符串列表，如果需要换行则要自己加入每行的换行符。
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