Python: File handling

In this post and subsequent posts, I am going to explain how to open, read and write to file.

How to open file

To read data from a file (or) to write data to a file, we need a reference object that points to file. ‘open’ method is used to get a file object.

open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

'open' function opens  file in specific mode and return corresponding file object. Throws OSError, if it is unable to open a file.

Parameter	Description
file	Full path of the file to be opened.
mode	Specifies the mode, in which the file is opened. By default file opens in read mode.
buffering	0: Switch off the buffer (only allowed in binary mode) 1: Line buffering (only usable in text mode) >1: Specify the size of buffer in bytes. If you don't specify any value, by default buffering works like below. a.   Binary files are buffered in fixed-size chunks; the size of the buffer is chosen using a heuristic trying to determine the underlying device’s “block size” and falling back on io.DEFAULT_BUFFER_SIZE. b.   “Interactive” text files use line buffering.
encoding	Type of encoding used to encode/decode a file. This value should be used in text mode. if encoding is not specified the encoding used is platform dependent.
errors	Specifies how encoding and decoding errors are to be handled. This cannot be used in binary mode
newline	controls how universal newlines mode works. A manner of interpreting text streams in which all of the following are recognized as ending a line: the Unix end-of-line convention '\n', the Windows convention '\r\n', and the old Macintosh convention '\r'.
closefd	If closefd is False and a file descriptor rather than a filename was given, the underlying file descriptor will be kept open when the file is closed. If a filename is given closefd must be True (the default) otherwise an error will be raised

Following are different modes that you can use while opening a file.

Mode	Description
'r'	open for reading
'w'	open for writing, truncating the file first
'x'	open for exclusive creation, failing if the file already exists
'a'	open for writing, appending to the end of the file if it exists
'b'	binary mode
't'	text mode (default)
'+'	open a disk file for updating (reading and writing)

For example, data.txt contains following data.

data.txt

First line

Second line

Third line

Fourth line

>>> f=open("/Users/harikrishna_gurram/data.txt")
>>> 
>>> f.read()
'First line\nSecond line\nThird line\nFourth line\n'

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