If size is specified, at most size bytes will be read. The line terminator is always b'n' for binary files; for text files, the newline argument to open can be used to select the line terminator(s) recognized. Readlines( hint-1 ) read and return a list of lines paperless 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. Note that its already possible to iterate on file objects using for line in file. Seek( offset, whence ) Change the stream position to the given byte offset. Offset is interpreted relative to the position indicated by whence. The default value for whence is seek_SET. Values for whence are: seek_set or 0 start of the stream (the default offset should be zero or positive seek_cur or 1 current stream position; offset may be negative seek_end or 2 end of the stream; offset is usually negative return the new absolute position.
An oserror is raised if the io object does not use a file descriptor. Flush Flush the write buffers of the stream if applicable. This does nothing for read-only and non-blocking streams. Isatty return True if the stream is interactive (i.e., connected to a terminal/tty device). Readable return True if the stream can be read from. If False, read will raise oserror. Readline( size-1 ) read and return one line from the stream.
Js, python, php, ruby
Lines are defined slightly differently depending on whether the stream is a binary stream (yielding bytes or a text stream (yielding character strings). Iobase is also a context manager and therefore supports the with statement. In this example, file is closed after the with statements suite is finished—even if an exception occurs: with open spam. Txt 'w as file: file. Write Spam and eggs! iobase provides these data pdf attributes and methods: close flush and close this stream.
This method has no effect if the file is already closed. Once the file is closed, any operation on the file (e.g. Reading or writing) will raise a valueError. As a convenience, it is allowed to call this method more business than once; only the first call, however, will have an effect. Closed True if the stream is closed. Fileno return the underlying file descriptor (an integer) of the stream if it exists.
The following table summarizes the abcs provided by the io module: abc inherits Stub Methods Mixin Methods and Properties iobase fileno, seek, and truncate close, closed, _enter _exit flush, isatty, _iter _next readable, readline, readlines, seekable, tell, writable, and writelines Rawiobase iobase readinto and write. I/o base Classes class Base The abstract base class for all I/O classes, acting on streams of bytes. There is no public constructor. This class provides empty abstract implementations for many methods that derived classes can override selectively; the default implementations represent a file that cannot be read, written or seeked. Even though iobase does not declare read readinto or write because their signatures will vary, implementations and clients should consider those methods part of the interface.
Also, implementations may raise a valueError (or UnsupportedOperation ) when operations they do not support are called. The basic type used for binary data read from or written to a file is bytes. Other bytes-like objects are accepted as method arguments too. In some cases, such as readinto, a writable object such as bytearray is required. Text I/O classes work with str data. Note that calling any method (even inquiries) on a closed stream is undefined. Implementations may raise valueError in this case. Iobase (and its subclasses) supports the iterator protocol, meaning that an iobase object can be iterated over yielding the lines in a stream.
Python - how do you append to a file?
Its subclasses, bufferedWriter, bufferedReader, and Bufferedrwpair buffer streams that are readable, writable, and both readable and writable. BufferedRandom provides a buffered interface to random access streams. Another Bufferediobase subclass, movie bytesio, is a stream of in-memory bytes. The textiobase abc, another subclass of iobase, deals with streams whose bytes represent text, and handles encoding and decoding to and from strings. TextIOWrapper, which extends it, is a buffered text interface to a buffered raw stream ( Bufferediobase ). Finally, stringio is an in-memory stream for text. Argument names are not part of the specification, and only the arguments of open are intended to be used as keyword arguments.
Note The abstract base classes also provide default implementations of some methods in order to help implementation of concrete stream solutions classes. For example, bufferediobase provides unoptimized implementations of readinto and readline. At the top of the I/O hierarchy is the abstract base class iobase. It defines the basic interface to a stream. Note, however, that there is no separation between reading and writing to streams; implementations are allowed to raise UnsupportedOperation if they do not support a given operation. The rawiobase abc extends iobase. It deals with the reading and writing of bytes to a stream. Fileio subclasses Rawiobase to provide an interface to files in the machines file system. The bufferediobase abc deals with buffering on a raw byte stream ( Rawiobase ).
manual control over the handling of text data is desired. The easiest way to create a binary stream is with open with 'b' in the mode string: f open g "rb In-memory binary streams are also available as Bytesio objects: f tesIO(b"some initial binary data: x00x01 The binary stream api is described in detail. Other library modules may provide additional ways to create text or binary streams. See kefile for example. Raw I/o raw I/O (also called unbuffered I/O ) is generally used as a low-level building-block for binary and text streams; it is rarely useful to directly manipulate a raw stream from user code. Nevertheless, you can create a raw stream by opening a file in binary mode with buffering disabled: f open g "rb buffering0) The raw stream api is described in detail in the docs of Rawiobase. Class hierarchy The implementation of I/O streams is organized as a hierarchy of classes. First abstract base classes (ABCs which are used to specify the various categories of streams, then concrete classes providing the standard stream implementations.
For example giving a str object to the write method of a binary stream will raise a typeError. So will giving a bytes object to the write method of a text stream. Changed in version.3: Operations that used to raise. Ioerror now raise, oserror, since, ioerror is now an alias of, oserror. Text I/O expects and produces str objects. This means that whenever the backing store is natively made of bytes (such as in the case of a file encoding and decoding of data is made transparently as well as optional translation of platform-specific newline characters. The easiest way to create a text stream is with gpa open, optionally specifying an encoding: f open myfile. Txt "r encoding"utf-8 In-memory text streams are also available as Stringio objects: f ringIO some initial text data the text stream api is described in detail in the documentation of Textiobase.
Linux by Examplesgrep multiple lines linux by Examples
Overview, the io module provides Pythons main facilities for dealing with various types of I/O. There are three main types of I/O: text I/o, binary I/O and raw I/O. These are generic categories, and various backing stores can be used for each of them. A concrete object belonging to any of these categories is called a file object. Other common terms are stream and file-like object. Independently of its category, each concrete stream object will also have various capabilities: it can be read-only, write-only, or read-write. It can also allow arbitrary random access (seeking forwards or backwards to any location or only sequential access (for example in the case of a socket or pipe). All hippie streams are careful about the type of data you give to them.