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
2. Binary Files

Usually, we use text files to store character data.

A text file stores data in the form of characters.

Examples include:

• Notes
• Logs
• Source code
• Configuration files

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.

These files are commonly used for multimedia and other non-text data.

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
• 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 → Name of the file.
• mode → Specifies how the file should be opened.

Python supports the following file modes.

Opens an existing file for reading.

Features

• File pointer is placed at the beginning of the file.
• If the file does not exist, Python raises:

• This is the default mode.

Opens a file for writing.

Features

• If the file already contains data, the existing data is overwritten.
• If the file does not exist, a new file is created.

Opens an existing file for appending data.

Features

• Existing data is not overwritten.
• New data is added at the end of the file.
• If the file does not exist, Python creates a new file.

Used to both read and write data.

Features

• Existing data is not deleted.
• File pointer is positioned at the beginning of the file.

Used for writing as well as reading.

Features

• Existing data is overwritten.

Used to append and read data.

Features

• Existing data is not overwritten.
• New data is appended to the file.

Used to create a new file for writing.

Features

• If the file already exists, Python raises:

All the above modes are applicable to text files.

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

The above statement opens the file abc.txt in write mode.

Mode	Description
r	Opens an existing file for reading.
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.

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.

Topic	Description
File Handling	Used to store data permanently.
Text File	Stores character data.
Binary File	Stores images, videos, audio, etc.
open()	Opens a file.
File Mode	Specifies how the file is opened.
Binary Mode	Text mode with b suffix.

1. Files are used to store data permanently.
2. There are two types of files: Text Files and Binary Files.
3. Before reading or writing, a file must be opened.
4. The open() function is used to open a file.
5. The file mode specifies the purpose of opening the file.
6. The default mode is r.
7. The w mode overwrites existing data.
8. The a mode appends new data without deleting existing data.
9. The x mode creates a new file and raises FileExistsError if the file already exists.
10. Adding b to a file mode makes it suitable for binary files.

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

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

The close() function closes the opened file after all file operations are completed.

Closing a file releases the resources associated with that file.

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

The following properties are available:

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.

Let's understand each statement used in the program.

Opens the file abc.txt in write mode.

The returned file object is stored in the variable f.

Returns the name of the opened file.

Returns the mode in which the file is opened.

Since the file is opened in write mode, it is not readable.

Since the file is opened in write mode, it is writable.

Before calling close(), the file is still open.

Closes the file after completing all file operations.

After calling close(), the file is closed.

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.

Topic	Description
close()	Closes the opened file.
name	Returns the file name.
mode	Returns the file mode.
closed	Indicates whether the file is closed.
readable()	Checks if the file is readable.
writable()	Checks if the file is writable.

1. After completing file operations, it is highly recommended to close the file.
2. The close() function is used to close an opened file.
3. name returns the name of the opened file.
4. mode returns the mode in which the file is opened.
5. closed returns False while the file is open and True after it is closed.
6. readable() returns whether the file supports reading.
7. writable() returns whether the file supports writing.

• Always close a file after completing all file operations.
• The close() function releases the file resources.
• A file object provides useful properties such as name, mode, closed, readable(), and writable().
• These properties help us understand the current status of the opened file.

1. Why should we close a file after completing file operations?
2. What is the purpose of the close() function?
3. What does the name property return?
4. What does the mode property return?
5. What is the difference between readable() and writable()?
6. When does the closed property return True?
7. Can we check whether a file is readable before performing read operations?
8. Which property tells us whether a file has already been closed?

We can read character data from a text file by using the following methods.

• read() → To read total data from the file.
• read(n) → To read n characters from the file.
• readline() → To read only one line.
• readlines() → To read all lines into a list.

Method	Purpose
read()	Reads the complete file.
read(n)	Reads a specified number of characters.
readline()	Reads one line.
readlines()	Reads all lines into a list.

The read() method is used to read the entire content of a text file.

The read() method returns all the data available in the file.

After reading the complete file, the file pointer moves to the end of the file.

Let's understand each statement in the program.

Opens the file abc.txt in read mode.

The file object is stored in the variable f.

The read() method reads the entire file content and stores it in the variable data.

The statement displays all the contents of the file.

Closes the file after completing the read operation.

The read(n) method is used to read the first n characters from the file.

• n represents the number of characters to be read.

Let's understand how the program works.

Opens the file in read mode.

The read(10) method reads only the first 10 characters from the file.

After reading those characters, the file pointer automatically moves to the next unread position.

Displays the first ten characters that were read from the file.

Closes the file after completing the operation.

Method	Description
read()	Reads the entire file.
read(n)	Reads only the specified number of characters.

Method	Purpose
read()	Reads the complete file content.
read(n)	Reads only the specified number of characters.

1. read() reads the entire content of the file.
2. read(n) reads only the specified number of characters.
3. The value of n represents the number of characters to read.
4. After reading data, the file pointer automatically moves forward.
5. Always close the file after completing file operations by using the close() function.

• Use read() when you want the complete file content.
• Use read(n) when you need only a specific number of characters.
• Both methods start reading from the current file pointer position.
• The file pointer automatically advances after every read operation.

1. What is the purpose of the read() method?
2. What is the difference between read() and read(n)?
3. What does the parameter n represent in read(n)?
4. What happens to the file pointer after calling read()?
5. Can read(n) read the complete file?
6. Why should the file be closed after reading?
7. Which mode should be used while reading a text file?
8. What is stored in the variable returned by read()?

In addition to reading the complete file or a specific number of characters, Python also provides methods to read data line by line.

The following methods are used for reading lines from a text file:

• readline() → Reads one line at a time.
• readlines() → Reads all lines and returns them as a list.

The readline() method is used to read only one line from a text file.

Each call to readline() reads the next line from the file.

After reading a line, the file pointer automatically moves to the beginning of the next line.

Let's understand how the program reads data line by line.

Reads the first line from the file.

Reads the second line from the file.

Reads the third line from the file.

Each call moves the file pointer to the beginning of the next line.

Closes the file after completing all read operations.

The readlines() method reads all lines from the file and returns them as a list.

Let's understand each statement used in the program.

Reads all lines from the file and stores them in the variable lines as a list.

The for loop prints each line one by one.

The end='' argument prevents printing an extra blank line.

Closes the file after reading all lines.

This example demonstrates how different reading methods work together while sharing the same file pointer.

Reads the first 3 characters from the file.

Reads the remaining characters of the current line.

Reads the next 4 characters from the current file pointer position.

Displays the message:

Reads all remaining data from the current file pointer position.

Method	Description
read()	Reads the complete file.
read(n)	Reads the specified number of characters.
readline()	Reads one line at a time.
readlines()	Reads all lines and returns a list.

Method	Purpose
read()	Reads complete file data.
read(n)	Reads specified number of characters.
readline()	Reads one line.
readlines()	Reads all lines into a list.

1. readline() reads only one line from the file at a time.
2. Each call to readline() moves the file pointer to the next line.
3. readlines() reads all lines from the file and returns them as a list.
4. read(), read(n), readline(), and readlines() start reading from the current file pointer position.
5. After each read operation, the file pointer automatically moves forward.
6. Always close the file after reading data.

• Use readline() when reading one line at a time.
• Use readlines() when all lines are required as a list.
• All reading methods use the same file pointer.
• Mixing different reading methods affects subsequent reads because the file pointer keeps moving forward.

1. What is the purpose of the readline() method?
2. What does the readlines() method return?
3. What is the difference between readline() and readlines()?
4. How does the file pointer behave after calling readline()?
5. Can read(), read(n), and readline() be used together?
6. Why is end='' used while printing lines?
7. Which method returns a list of lines?
8. Why should a file be closed after reading?

We can write character data to text files by using the following two methods:

• write(str)
• writelines(list of lines)

Method	Purpose
write(str)	Writes a single string to a text file.
writelines(list)	Writes multiple strings from a list into a text file.

The write() method is used to write character data to a text file.

• str represents the string to be written into the file.

Let's understand how the above program writes data into the file.

Opens the file abcd.txt in write mode.

If the file already exists, its previous contents are overwritten.

If the file does not exist, Python automatically creates a new file.

Writes the first line into the file.

The \n moves the cursor to the next line.

Writes the second line into the file.

Writes the third line into the file.

Displays a confirmation message after successfully writing data to the file.

Closes the file after completing the write operation.

In the above program, if we execute the program again, the existing data in the file will be overwritten every time.

Instead of overwriting, if we want to append data, then we should open the file as follows:

Opening a file in a (append) mode preserves the existing contents and adds the new data at the end of the file.

The writelines() method is used to write multiple lines from a list into a text file.

Let's understand how the writelines() method works.

Creates a list containing four strings.

Notice that the first three strings contain the newline character (\n), while the last string does not.

Writes all strings from the list into the file.

Each string is written in the same order as it appears in the list.

Method	Description
write(str)	Writes a single string to the file.
writelines(list)	Writes multiple strings from a list.

Method	Purpose
write()	Writes a single string to the file.
writelines()	Writes multiple strings from a list.

1. We can write character data to text files by using write() and writelines().
2. write() writes a single string to the file.
3. writelines() writes multiple strings from a list.
4. Opening a file in w mode overwrites the existing data.
5. To append data instead of overwriting, open the file in a mode.
6. The writelines() method writes all strings from the given list into the file in sequence.

• Use write() to write a single string.
• Use writelines() to write multiple strings from a list.
• w mode replaces existing file contents.
• a mode preserves old data and appends new data.
• Always close the file after writing.

1. What is the purpose of the write() method?
2. What is the purpose of the writelines() method?
3. What is the difference between write() and writelines()?
4. What happens if a file is opened in w mode?
5. Which mode should be used to append data without deleting existing data?
6. Can writelines() write multiple strings at once?
7. Why is close() called after writing to a file?
8. What happens if the file specified in write mode does not already exist?

When writing data by using the write() method, we must provide the line separator \n.

Otherwise, all the data will be written into a single line.

The newline character (\n) tells Python to move the cursor to the next line after writing the current string.

If the newline character is omitted, the next string is written immediately after the previous string without any line break.

The following program writes data without using the newline character.

Let's understand why all the text appears on a single line.

Opens the file abcd.txt in write mode.

Writes the string Durga into the file.

Since there is no \n, the cursor remains on the same line.

The string Software is written immediately after Durga.

No space or new line is added automatically.

The string Solutions is written immediately after Software.

As a result, all three strings appear continuously in a single line.

Closes the file after completing the write operation.

Since the newline character (\n) is not used, all the strings are written continuously in a single line.

The following program uses the newline character while writing each string.

Let's understand why each string appears on a separate line.

Writes Durga and then moves the cursor to the next line.

Writes Software on the next line and again moves the cursor to the following line.

Writes Solutions on the next available line.

Each call to write() includes the newline character (\n), so every string is written on a separate line.

Method / Symbol	Purpose
write()	Writes a string to a file.
\n	Moves the cursor to the next line.
writelines()	Writes multiple strings from a list.

1. While using the write() method, we must provide the newline character (\n) if each string should appear on a separate line.
2. If \n is not used, all strings are written in a single line.
3. The writelines() method writes the strings exactly as they are provided in the list.
4. If newline characters are required while using writelines(), they must be included in each string of the list.

• write() does not automatically insert a new line.
• The newline character (\n) is responsible for moving the cursor to the next line.
• Without \n, all strings are written continuously.
• When using writelines(), newline characters must be included manually if line breaks are required.

1. Why is the newline character (\n) required while using write()?
2. What happens if \n is not used?
3. Does the write() method automatically move to the next line?
4. How does writelines() handle newline characters?
5. What is the difference between writing with and without \n?
6. Can multiple strings be written on separate lines without using \n?
7. Why do all strings appear on a single line in some programs?
8. Which symbol is used to move the cursor to the next line in Python?

This completes the Writing Data to Text Files section of the File Handling chapter.

The following topics have been covered:

• ✅ write() method
• ✅ writelines() method
• ✅ Writing a single string
• ✅ Writing multiple lines
• ✅ Append mode (a)
• ✅ Importance of the newline character (\n)

Before performing operations on a file, it is a good programming practice to check whether the file exists.

If we try to open a file that does not exist in read (r) mode, Python raises a FileNotFoundError.

To avoid this error, Python provides the os.path.isfile() function.

The os.path.isfile() function checks whether the specified file exists.

• Returns True if the specified file exists.
• Returns False if the file does not exist.

Let's understand each statement used in the program.

The os module provides various functions for interacting with the operating system.

The path.isfile() function belongs to this module.

Accepts the file name from the user at runtime.

If the specified file exists, the condition becomes True.

Otherwise, it becomes False.

Displays the appropriate message based on whether the file exists.

Checking whether a file exists helps prevent runtime errors.

It also allows the program to handle missing files gracefully instead of terminating unexpectedly.

The following program reads a text file and counts:

• Total number of lines
• Total number of words
• Total number of characters

Let's understand how the program calculates the number of lines, words, and characters.

Three variables are initialized to zero.

• lcount → Counts the number of lines.
• wcount → Counts the number of words.
• ccount → Counts the number of characters.

The for loop reads one line at a time from the file.

Each iteration represents one line, so the line counter is incremented by one.

The split() method separates the line into individual words.

It returns a list containing all the words in that line.

The number of words in the current line is added to the total word count.

The len(line) function returns the number of characters in the current line.

The result is added to the total character count.

Function / Method	Purpose
os.path.isfile()	Checks whether a file exists.
split()	Splits a line into words.
len()	Returns the number of characters or list elements.
for line in file	Reads one line at a time.

1. Always check whether a file exists before opening it in read mode.
2. os.path.isfile() returns True only if the specified file exists.
3. The split() method separates a line into individual words.
4. len() is used to count words and characters.
5. Reading a file line by line is memory efficient for large files.
6. Always close the file after completing all file operations.

• Use os.path.isfile() to verify file existence.
• Checking file existence prevents FileNotFoundError.
• Use split() to separate words in a line.
• Use len() to count lines, words, and characters.
• Process files line by line using a for loop.

1. Why should we check whether a file exists before opening it?
2. What is the purpose of os.path.isfile()?
3. What values can os.path.isfile() return?
4. How can you count the number of lines in a text file?
5. How can you count the number of words in a file?
6. How can you count the number of characters in a file?
7. What is the purpose of the split() method?
8. Why is the len() function used in this program?

Until now, we have worked with text files. Python also supports working with binary files.

Binary files are used to store non-text data such as:

• Images
• Audio files
• Video files
• PDF documents
• Executable files

While working with binary files, the file should be opened in binary mode by using rb, wb, ab, etc.

Mode	Description
rb	Read binary file.
wb	Write binary file.
ab	Append binary data.
rb+	Read and write binary file.
wb+	Write and read binary file.
ab+	Append and read binary file.

The following program copies the contents of one image file into another image file.

Let's understand each statement in the program.

Opens the source image in read binary mode.

The image data can now be read as binary bytes.

Reads the complete binary contents of the image.

The binary data is stored in the variable data.

Creates a new binary file in write mode.

If the file already exists, its contents will be overwritten.

Writes all binary data into the new image file.

The copied image will be exactly the same as the original image.

Both source and destination files are closed after the copy operation is completed.

CSV stands for Comma Separated Values.

A CSV file is used to store tabular data such as:

• Student records
• Employee records
• Sales reports
• Product information

Each row in a CSV file represents one record, and each value is separated by a comma.

Python provides the built-in csv module for working with CSV files.

To write data into a CSV file, we use the csv.writer() function.

The writerow() method writes a single record into the CSV file.

Let's understand how the CSV writing program works.

Creates the CSV file in write mode.

The parameter newline='' prevents blank lines from appearing between records.

Creates a CSV writer object that is responsible for writing records into the CSV file.

Writes the column headings into the CSV file.

Each call to writerow() writes one employee record into the CSV file.

Function / Method	Purpose
rb	Read binary file.
wb	Write binary file.
csv.writer()	Creates a CSV writer object.
writerow()	Writes one record into the CSV file.
newline=''	Prevents blank lines in CSV files.

1. Binary files store non-text data such as images, videos, and audio files.
2. Always use binary modes (rb, wb, etc.) while working with binary files.
3. The csv module is used to work with CSV files.
4. csv.writer() creates a writer object.
5. writerow() writes one record at a time.
6. Always use newline='' while opening a CSV file for writing.
7. Always close the file after completing file operations.

• Binary files are used for storing images, videos, audio, and other binary data.
• Use rb to read and wb to write binary files.
• CSV stands for Comma Separated Values.
• Use the csv module to create and manage CSV files.
• Use writerow() to insert one record into a CSV file.

1. What is a binary file?
2. Which file modes are used for binary files?
3. How can you copy one image file to another in Python?
4. What does CSV stand for?
5. What is the purpose of the csv module?
6. What does csv.writer() return?
7. What is the purpose of the writerow() method?
8. Why is newline='' used while creating CSV files?

Python provides the csv.reader() function to read data from a CSV file.

The reader() function reads one record at a time and returns each record as a list.

To read records from a CSV file, we first create a reader object by using the csv.reader() function.

Let's understand how the program reads records from a CSV file.

The csv module provides functions for reading and writing CSV files.

Opens the CSV file in read mode.

Creates a CSV reader object.

The reader object reads one record at a time from the CSV file.

The for loop reads every record in the file.

Each record is returned as a list of column values.

Closes the CSV file after completing the read operation.

A ZIP file is a compressed file that can store one or more files and folders.

Compression reduces the file size, making it easier to store and transfer files.

Python provides the built-in zipfile module for creating, reading, and extracting ZIP files.

• Reduces file size.
• Saves storage space.
• Makes file transfer faster.
• Allows multiple files to be stored in a single archive.
• Easy to share files over the Internet.

Python provides the zipfile module to perform ZIP file operations.

The ZipFile class is used to create, read, and extract ZIP files.

Parameter	Description
file_name	Name of the ZIP file.
mode	Specifies how the ZIP file should be opened.
compression	Specifies the compression method.

The most commonly used compression constants are:

Constant	Description
ZIP_STORED	No compression is applied.
ZIP_DEFLATED	Compresses files to reduce their size.

ZIP_DEFLATED is the most commonly used compression method.

It compresses the file before storing it inside the ZIP archive, thereby reducing the file size.

• Backing up files.
• Sending multiple files through email.
• Reducing storage space.
• Distributing software packages.
• Archiving project folders.

Function / Class	Purpose
csv.reader()	Reads records from a CSV file.
ZipFile	Creates, reads, and extracts ZIP files.
ZIP_STORED	Stores files without compression.
ZIP_DEFLATED	Compresses files before storing them.

1. csv.reader() is used to read records from a CSV file.
2. Each record is returned as a list.
3. The zipfile module provides support for ZIP file operations.
4. The ZipFile class is the main class used for ZIP file handling.
5. ZIP_DEFLATED performs file compression.
6. ZIP_STORED stores files without compression.
7. ZIP files reduce storage space and simplify file sharing.

• Use csv.reader() to read CSV files.
• Each CSV row is returned as a list.
• Use the zipfile module for ZIP file operations.
• The ZipFile class handles ZIP archives.
• ZIP_DEFLATED compresses files, while ZIP_STORED does not.

1. What is the purpose of the csv.reader() function?
2. What does each record returned by csv.reader() contain?
3. What is a ZIP file?
4. Which Python module is used for ZIP file handling?
5. What is the purpose of the ZipFile class?
6. What is the difference between ZIP_STORED and ZIP_DEFLATED?
7. Why are ZIP files commonly used?
8. What are the advantages of compressing files?

Python provides the built-in zipfile module to create ZIP files.

To create a ZIP file, we create a ZipFile object in write mode by using the ZIP_DEFLATED compression constant.

Let's understand each statement in the program.

Imports all classes, constants, and functions from the zipfile module.

Creates a ZIP file named files.zip.

• "w" opens the ZIP file in write mode.
• ZIP_DEFLATED indicates that the files should be compressed before being stored.

The write() method adds each specified file into the ZIP archive.

Each call inserts one file into the ZIP file.

Closes the ZIP file after adding all files.

To read or extract information from an existing ZIP file, create a ZipFile object in read mode.

ZIP_STORED represents the unzip operation.

It is the default value, so specifying it is optional.

After opening the ZIP file, we can obtain the names of all files stored inside it by using the namelist() method.

The following steps explain how the ZIP archive is processed.