Seek Function in Python

Last Updated on November 1, 2023 by Ankit Kochar

Python is renowned for its simplicity and versatility, making it a popular choice for developers of all levels. While many Python functions are intuitive and straightforward, some may appear more complex at first glance. One such function is the seek function in python. In this comprehensive guide, we aim to demystify the seek function in Python, explaining its purpose, usage, and practical applications. Whether you’re a novice or an experienced programmer, understanding seek is essential for mastering file handling and manipulation in Python. So, let’s dive into the world of seek and unlock the power it holds for your Python projects.

What is a Seek Function in Python?

The seek function is a built-in function in Python that is used to set the current position of the file pointer within a file. The file pointer is a marker that indicates the current position in the file, and it is used to read or write data from that point. This function is particularly useful when reading or writing large files, as it allows us to move the file pointer to a specific location within the file and read or write data from that point.

Syntax of Seek Function in Python

The syntax of the seek function in Python is as follows:

file.seek(offset, whence) 

Here, file is the file object that we want to set the position of the file pointer in.

Parameters of Seek Function in Python

The first argument, offset, is the number of bytes we want to move the file pointer. The second argument, whence, specifies the reference position from where we want to move the file pointer. The possible values of whence are

• 0 (default): refers to the beginning of the file
• 1: refers to the current position of the file pointer
• 2: refers to the end of the file

Example of Seek Function in Python

Let’s see an example of how to use the seek function to set the position of the file pointer within a file:

data.txt File:

PrepBytes is an Ed-Tech Company.

Code:

# Open a file in read mode
file = open("data.txt", "r")

# Set the position of the file pointer to byte 10
file.seek(10)

# Read the next 5 bytes from the file
data = file.read(5)

# Print the data that was read
print(data)

# Close the file
file.close()

Output:

is an

Explanation:
In this example, we opened a file called data.txt in read mode and set the position of the file pointer to byte 10 using the seek function. We then read the next 5 bytes from the file using the read function and printed the data that was read which gives us an output as “is an”. Finally, we closed the file using the close function.

Different Modes of the Seek Function in Python

The seek function can be used in three different modes: absolute mode, relative mode, and from end mode. Let’s see each of these modes in detail:

Absolute Mode

In absolute mode, the offset parameter specifies the number of bytes from the start of the file where we want to set the file pointer. In other words, the file pointer is set to an absolute position within the file.

The syntax for using the seek function in python in absolute mode is as follows:

file.seek(offset, 0)

Here, the second parameter is 0, which specifies that we want to set the file pointer in absolute mode.

Let’s see an example of how to use the seek function in absolute mode:

data.txt File:

PrepBytes is an Ed-Tech Company.

Code:

# Open a file in read mode
file = open("data.txt", "r")

# Set the position of the file pointer to byte 10
file.seek(10, 0)

# Read the next 5 bytes from the file
data = file.read(5)

# Print the data that was read
print(data)

# Close the file
file.close()

Output:

is an

Relative Mode

In relative mode, the offset parameter specifies the number of bytes to move the file pointer from its current position. In other words, the file pointer is set to a position relative to its current position.

The syntax for using the seek function in relative mode is as follows:

file.seek(offset, 1) 

Here, the second parameter is 1, which specifies that we want to set the file pointer in relative mode.

Let’s see an example of how to use the seek function in relative mode:

data.txt File:

PrepBytes is an Ed-Tech Company.

Code:

# Open a file in read mode
file = open("data.txt", "r")

# Set the position of the file pointer to 10 bytes from the current position
file.seek(10, 1)

# Read the next 5 bytes from the file
data = file.read(5)

# Print the data that was read
print(data)

# Close the file
file.close()

Output:

is an

Explanation:
In this example, we opened a file called data.txt in read mode and set the position of the file pointer to 10 bytes from its current position using the seek function in relative mode. We then read the next 5 bytes from the file using the read function and printed the data that was read. Finally, we closed the file using the close function.

From End Mode

In from end mode, the offset parameter specifies the number of bytes from the end of the file where we want to set the file pointer. In other words, the file pointer is set to a position relative to the end of the file.

The syntax for using the seek function in from end mode is as follows:

file.seek(offset, 2)

Here, the second parameter is 2, which specifies that we want to set the file pointer in from end mode.

Let’s see an example of how to use the seek function in from end mode:

data.txt File:

PrepBytes is an Ed-Tech Company.

Code:

# Open a file in read mode
file = open("data.txt", "r")

# Set the position of the file pointer to 10 bytes from the end of the file
file.seek(-10, 2)

# Read the next 5 bytes from the file
data = file.read(5)

# Print the data that was read
print(data)

# Close the file
file.close()

Output:

h Com

Explanation:
In this example, we opened a file called data.txt in read mode and set the position of the file pointer to 10 bytes from the end of the file using the seek function in from end mode. We then read the next 5 bytes from the file using the read function and printed the data that was read. Finally, we closed the file using the close function.

Using the Tell Function

The tell function is another built-in function in Python that is used to get the current position of the file pointer within a file.

The syntax of the tell function is as follows:

file.tell() 

Here, file is the file object for which we want to get the current position of the file pointer.

Let’s see an example of how to use the tell function:

data.txt File:

PrepBytes is an Ed-Tech Company.

Code:

# Open a file in read mode
file = open("data.txt", "r")

# Get the current position of the file pointer
position = file.tell()

# Print the current position of the file pointer
print(position)

# Close the file
file.close()

Output:

0

Explanation:
In this example, we opened a file called data.txt in read mode and used the tell function to get the current position of the file pointer. We then printed the current position of the file pointer which shows “0” on the console and closed the file using the close function.

Conclusion
In conclusion, the seek function in Python is a crucial tool for working with files. It allows you to control the position of the file pointer, enabling efficient reading, writing, and manipulation of file contents. By grasping the concepts outlined in this guide, you’ve taken a significant step towards becoming a proficient Python programmer. You now have the knowledge to harness the seek function’s power and apply it to various real-world scenarios, from data processing to log analysis. With practice, you’ll become more comfortable and proficient in using seek, further enhancing your Python programming skills.

Remember that seek is just one of the many file handling tools Python offers. Continuously exploring the language and its libraries will open up endless possibilities for your coding projects. Whether you’re a beginner or a seasoned developer, the seek function, along with the broader Python ecosystem, offers limitless potential.

Seek Function in Python – FAQs

Here are some FAQs related to Python seek Function.

1. Can I seek in read-only files or directories?
No, the seek function is designed for seeking within files that can be read and written, not read-only files or directories. Attempting to use seek on read-only files or directories will result in an error.

2. How do I use the seek function in Python?
To use the seek function, you first need to open a file using the open() function and a suitable file mode. Once the file is open, you can apply the seek function with the desired offset and reference point. For example, file.seek(offset, whence) allows you to move the file pointer to the specified offset relative to the reference point (beginning, current position, or end of the file).

3. What are the common use cases for the seek function?
The seek function is commonly used when you need to read or modify specific portions of a file. It’s helpful for tasks like extracting data from a certain location in a file, updating specific information, or navigating large files efficiently. It’s widely used in data processing, log file analysis, and more.

4. What are the reference points (whence) in the seek function?
The whence parameter in the seek function can take three values: 0 (beginning of the file), 1 (current position), and 2 (end of the file). These values determine the reference point for the offset provided, allowing you to seek to a specific location in the file.

5. Can I seek in both text and binary files?
Yes, you can use the seek function in both text and binary files. However, you need to be aware of the differences in how these types of files handle line endings (e.g., newline characters) to avoid unexpected behavior when seeking in text files. Binary mode is often preferred for precise control.

6. Are there any risks in using the seek function?
Using the seek function can be risky if you’re not careful, as it can lead to unexpected results or data corruption. Make sure to handle exceptions, check file boundaries, and maintain good practices to minimize the risks. Always back up important data before making extensive file modifications.