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Python: open() function

open() function

The open() function is used to open a file and returns it as a file object.

Version:

(Python 3.2.5)

Syntax:

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

Parameter:

Name Description Required /
Optional
file path-like object (representing a file system path) giving the pathname. Required
mode
Character Meaning
'r' open for reading (default)
'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)
'U' universal newlines mode (deprecated)
Optional
buffering Set buffering policy. Optional
encoding Encode or decode the file. Optional
error String specifying how to handle encoding/decoding errors. Optional
newline how newlines mode works (available values: None, ' ', '\n', 'r', and '\r\n'. Optional
closefd True. If a file descriptor is given, it is closed when the returned I/O object is closed, unless closefd is set to False. Optional
opener A custom opener can be used by passing a callable as opener. Optional

Return value:

Returns a file object which can used to read, write and modify file.

Example: Python open() function

# opens example.text file of the current directory
x = open("example.txt")
print(open("example.txt"))

Create file: example.txt

Twinkle, twinkle, little star,
	How I wonder what you are! 
		Up above the world so high,   		
		Like a diamond in the sky. 
Twinkle, twinkle, little star, 
	How I wonder what you are!

Output:

<_io.TextIOWrapper name='example.txt' mode='r' encoding='UTF-8'>

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Python: Tips of the Day

Find current directory and file's directory:

To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

  • The os and os.path modules.
  • The __file__ constant
  • os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
  • os.path.dirname(path) (returns "the directory name of pathname path")
  • os.getcwd() (returns "a string representing the current working directory")
  • os.chdir(path) ("change the current working directory to path")

Ref: https://bit.ly/3fy0R6m