python 3-5-1 关于文件的操作-open/read/readlines/seek/write/writelines

关于文件的操作

f = open(“test.sh”) f是一个可迭代对象
readlines() 方法是将文件的所有内容放进列表中,如果文件非常大，内存消耗是个极大的问题
readline() 既然open()返回的是一个可迭代对象,则可以用for循环来逐行取出
seek() 当readlines 或者readline迭代结束以后，文件的指针就指向了文件尾，可以通过f.seek(0)将文件指针指向文件头
read()读取字节数，如果没有给定字节数，则会直接读到最后
write() 写入字符串到文件
writelines()写入多行字符串到文件

from collections import Iterableisinstance(f,Iterable)f = open("test.sh")for line in f:     print line

关于文件操作帮助信息

>>> help(f)Help on file object: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 size.  The preferred way |  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([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. |   |  readinto(...) |      readinto() -> Undocumented.  Don't use this; it may go away. |   |  readline(...) |      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. |   |  readlines(...) |      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. |   |  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. |   |  tell(...) |      tell() -> current file position, an integer (may be a long integer). |   |  truncate(...) |      truncate([size]) -> None.  Truncate the file to at most size bytes. |       |      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