how-to-open-a-file-object.md

author	type	category	links	practiceQuestion	revisionQuestion
SebaRaba	normal	how-to	[More about open() function](https://www.tutorialspoint.com/python3/python_files_io.htm){website}	formats context fill-in-the-gap type-in-the-gap standalone	formats context fill-in-the-gap type-in-the-gap standalone

How to open a file object

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Content

Reading from and writing to files in Python 3 can be done using the open() function. This will create a file object, which can be used to call other support methods associated with it.

Consider the following syntax:

obj = open(f_name, [access_mode],
                      [buffering])

Here's the disambiguation of its arguments:

• f_name: string value that contains the name of the file
• access_mode: it determines the mode in which the file has to be opened: read, write, append
• buffering: there are two important values 0 (means no buffering) or 1 (means line buffering is performed). If the value is greater than 1 then that will be considered the buffer's size

The supported modes for opening a file are:

• a: Opens the file for appending. With the file pointer being at the end of the file
• r: Opens the file for reading. With the file pointer being at the beginning of the file
• w: Opens the file for writing. Overwrites the file if it exists. If the file doesn't exist it will create a new file
• a+: Opens the file for both reading and appending. The file pointer is at the end of the file
• r+: Opens the file for both reading and writing. The file pointer is place at the beginning of the file
• w+: Opens the file for writing and reading as well. Overwrites the existing file. If it doesn't exist, creates a new file
• ab/rb/wb: Opens the file for appending/reading/writing in binary format

Always pay attention to where the file pointer is. That is mainly because when we append something a to a file the pointer stays at the end of the file. If we want to print it we need to bring the pointer back to the beginning. This can be done using seek() method (eg. seek(0) will move the pointer to the beginning of the file.)

Note that every file object has the following attributes:

• file.closed: returns true if the file is closed and false otherwise
• file.mode: returns which mode the file was opened in
• file.name: returns the name of the file

Consider the following example:

# Open file.txt and print file name

obj = open("doc.txt","w")
print("The file name is: ", obj.name)
# Output: The file name is: doc.txt

print("The file mode is: ", obj.mode)
# Output: The file mode is: w
# this means write

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Practice

Suppose we want to open a file for both reading and appending. Fill the gaps accordingly:

file = open('practice.py', 'a')
file.write('Append this')
file.seek(0)

• open
• a+
• seek
• a
• write
• append
• w

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Revision

Suppose we want to open a file and write something to it. Fill the gaps accordingly:

file = open('practice.txt', '???')
file.???('this is my new file')

• w
• write
• r
• read