seek() function in Python

In Python, the seek() function is used to move the file cursor to a specific position inside a file. This allows you to read or write at any part of the file instead of always starting from the beginning. For example, if you want to skip the first 10 characters while reading a file, you can do: 

f = open("demo.txt", "r")
f.seek(10)
print(f.read())
f.close()

This will move the file cursor to position 10 and begin reading from there.

Syntax: 

file.seek(offset, from_what)

Parameters:

• offset: Number of bytes to move the cursor.
• from_what: (optional) Reference point to start from:
  • 0: sets the reference point at the beginning of the file 
  • 1: sets the reference point at the current file position 
  • 2: sets the reference point at the end of the file 

Returns:

• Returns the new absolute cursor position from the beginning.

Note: In text mode, from_what can only be 0. Using 1 or 2 requires binary mode ('rb').

Examples

Example 1: Using seek() in Text Mode

Let's say GfG.txt contains:

Code is like humor. When you have to explain it, it’s bad.

f = open("GfG.txt", "r")

f.seek(20)
print(f.tell())
print(f.readline())

f.close()

Output:

20
When you have to explain it, it’s bad.

Explanation:

• seek(20) moves the cursor to character 20.
• tell() confirms the cursor is at position 20.
• readline() reads from that position onward.

Example 2: Using seek() in Binary Mode with Negative Offset

Suppose data.txt contains the following binary content:

b'Code is like humor. When you have to explain it, its bad.'

f = open("data.txt", "rb")

f.seek(-10, 2)
print(f.tell())
print(f.readline().decode('utf-8'))

f.close()

Output:

47
, its bad.

Explanation:

• File is opened in binary mode ('rb').
• seek(-10, 2) moves 10 bytes before the end of the file.
• readline() reads from that point to the end.
• Output is decoded from binary to string.

Refer the below article to understand the basics of File Handling. 

• File Handling in Python. 
• Reading and Writing to files in Python