Question

我想指定一个偏移量，然后读取像

这样的文件的字节

offset = 5
read(5)

然后阅读接下来的6-10等我读到了关于搜索但我无法理解它是如何工作的并且这些例子不够描述。

seek(offset,1)返回什么？

由于

Answer 1

只需使用Python的REPL来亲眼看看：

[...]:/tmp$ cat hello.txt 
hello world
[...]:/tmp$ python
Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> f = open('hello.txt', 'rb')
>>> f.seek(6, 1)    # move the file pointer forward 6 bytes (i.e. to the 'w')
>>> f.read()        # read the rest of the file from the current file pointer
'world\n'

Answer 2

seek的第二个参数的值为0,1或2：

0 - offset is relative to start of file
1 - offset is relative to current position
2 - offset is relative to end of file

请记住，您可以查看帮助 -

>>> 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.

Answer 3

seek没有任何有用的东西。它只是将内部文件指针移动到给定的偏移量。下一次读取将从该指针开始读取。

在python中读取文件的特定字节

3 个答案: