Python open()

The open() function opens the file (if possible) and returns the corresponding file object.

The syntax of open() is:

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

1. open() Parameters

• file – path-like object (representing a file system path)
• mode (optional) – mode while opening a file. If not provided, it defaults to 'r' (open for reading in text mode). Available file modes are:ModeDescription'r'Open a file for reading. (default)'w'Open a file for writing. Creates a new file if it does not exist or truncates the file if it exists.'x'Open a file for exclusive creation. If the file already exists, the operation fails.'a'Open for appending at the end of the file without truncating it. Creates a new file if it does not exist.'t'Open in text mode. (default)'b'Open in binary mode.'+'Open a file for updating (reading and writing)
• buffering (optional) – used for setting buffering policy
• encoding (optional) – the encoding format
• errors (optional) – string specifying how to handle encoding/decoding errors
• newline​ (optional) – how newlines mode works (available values: None, ' ', '\n', 'r', and '\r\n'
• closefd (optional) – must be True (default); if given otherwise, an exception will be raised
• opener (optional) – a custom opener; must return an open file descriptor

2. Return Value from open()

The open() function returns a file object which can used to read, write and modify the file.

If the file is not found, it raises the FileNotFoundError exception.

3. Example 1: How to open a file in Python?

# opens test.text file of the current directory
f = open("test.txt")

# specifying the full path
f = open("C:/Python33/README.txt")

Since the mode is omitted, the file is opened in 'r' mode; opens for reading.

4. Example 2: Providing mode to open()

# opens the file in reading mode
f = open("path_to_file", mode='r')

# opens the file in writing mode 
f = open("path_to_file", mode = 'w')

# opens for writing to the end 
f = open("path_to_file", mode = 'a')

Python’s default encoding is ASCII. You can easily change it by passing the encoding parameter.

f = open("path_to_file", mode = 'r', encoding='utf-8')

Recommended Reading: Python File Input/Output