Python - File Handling

As part of programming requirements, we have to store our data permanently for future use.

For this requirement, we should use files.

Files are very common permanent storage areas used to store data.

Normally, the data stored in variables exists only while the program is running.

When the program terminates, that data is lost.

To store data permanently so that it can be used again in the future, Python provides File Handling.

Using files, we can save information permanently and access it whenever required.

There are two types of files.

1. Text Files - used to store character data.
2. Binary Files - used to store binary data such as images, videos, and audio.

Usually, we use text files to store character data.

Examples include:

• Notes
• Logs
• Source code
• Configuration files

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Usually, we use binary files to store binary data such as:

• Images
• Video files
• Audio files

Binary files store data in binary format instead of plain characters.

Text Files	Binary Files
Stores character data	Stores binary data
Human readable	Not directly human readable
Example: abc.txt	Examples: Images, Videos, Audio files

Before performing any operation such as reading or writing, we must first open the file.

For this purpose, Python provides the built-in open() function.

At the time of opening the file, we must specify the mode, which represents the purpose of opening the file.

• filename - the name of the file.
• mode - specifies how the file should be opened.

The above statement opens the file abc.txt in write mode and stores the file object in the variable f.

Python supports the following file modes.

1. Read Mode (r) - opens an existing file for reading. The file pointer is placed at the beginning. If the file does not exist, Python raises FileNotFoundError. This is the default mode.
2. Write Mode (w) - opens a file for writing. If the file already contains data, the existing data is overwritten. If the file does not exist, a new file is created.
3. Append Mode (a) - opens an existing file for appending data. Existing data is not overwritten; new data is added at the end. If the file does not exist, Python creates a new file.
4. Read and Write Mode (r+) - used to both read and write data. Existing data is not deleted and the file pointer is positioned at the beginning.
5. Write and Read Mode (w+) - used for writing as well as reading. Existing data is overwritten.
6. Append and Read Mode (a+) - used to append and read data. Existing data is not overwritten.
7. Exclusive Creation Mode (x) - used to create a new file for writing. If the file already exists, Python raises FileExistsError.

Mode	Description
r	Opens an existing file for reading (default mode).
w	Opens a file for writing and overwrites existing data.
a	Opens a file for appending data.
r+	Reads and writes without deleting existing data.
w+	Writes and reads; existing data is overwritten.
a+	Appends and reads without overwriting existing data.
x	Creates a new file exclusively for writing.

All the above modes are applicable to text files.

If we suffix the mode with b, then it represents a binary file.

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Mode	Description
rb	Read binary file.
wb	Write binary file.
ab	Append binary file.
r+b	Read and write binary file.
w+b	Write and read binary file.
a+b	Append and read binary file.
xb	Create a new binary file.

After completing all operations on a file, it is highly recommended to close the file.

For this purpose, we use the close() function.

Closing a file releases the resources associated with that file.

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Once a file is opened and we get a file object, we can access several properties related to that file.

Property / Method	Description
name	Returns the name of the opened file.
mode	Returns the mode in which the file is opened.
closed	Returns True if the file is closed; otherwise False.
readable()	Returns True if the file is readable.
writable()	Returns True if the file is writable.

The following program demonstrates how to access different properties of a file object.

File Name: abc.txt
File Mode: w
Is File Readable: False
Is File Writable: True
Is File Closed : False
Is File Closed : True

Let's understand the output of the above program:

• f.name returns abc.txt because the file is opened with that name.
• f.mode returns w because the file is opened in write mode.
• f.readable() returns False because write mode does not support reading.
• f.writable() returns True because write mode supports writing.
• f.closed returns False before close() is called and True after it.

Property	Returns
f.name	Name of the file.
f.mode	File opening mode.
f.closed	True if closed; otherwise False.
f.readable()	Whether the file can be read.
f.writable()	Whether the file can be written.