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tell() & seek() methods

Here is a clear, simple, and exam-focused explanation of tell() and seek() methods in Python file handling

⭐ tell() and seek() Methods in Python

When working with files, Python maintains an internal file pointer (cursor) that indicates the current read/write position in the file.

  • tell() → shows the current position of the file pointer
  • seek() → moves the file pointer to a specific position

These methods help in navigating through the file.

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⭐ 1. tell() Method

✔ Purpose:

Returns the current position of the file pointer.

File positions start from 0 (beginning of file).

✔ Syntax

file_object.tell()

✔ Example

f = open("data.txt", "r")
print(f.tell())     # Output: 0 (start of file)
f.read(5)
print(f.tell())     # Output: 5 (after reading 5 characters)
f.close()

📌 After every read/write operation, the file pointer moves forward.

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⭐ 2. seek() Method

✔ Purpose:

Moves the file pointer to a specified position.

✔ Syntax

file_object.seek(offset, from_where)

Parameters

  1. offset → number of bytes to move
  2. from_where (optional):
    • 0 → from beginning of file (default)
    • 1 → from current position
    • 2 → from end of file

⭐ Examples of seek()

✔ Example 1: Move to beginning of file

f = open("data.txt", "r")
f.seek(0)    # moves cursor to start

✔ Example 2: Move to 10th character

f = open("data.txt", "r")
f.seek(10)
print(f.read())   # reads from 10th character onward

✔ Example 3: Move forward from current position

f = open("data.txt", "r")
f.seek(5)           # move to 5th character
print(f.read(5))    # read next 5 characters
f.seek(2, 1)        # move 2 characters ahead from current position
print(f.read(5))

✔ Example 4: Move to end of file

f = open("data.txt", "rb")   # must use binary mode for 'from end'
f.seek(0, 2)   # move to end of file
print(f.tell())  # position at end

⚠ In text mode, only seek(offset, 0) and seek(offset, 2) (with offset=0) are reliable.
Binary mode allows full use of seek().

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⭐ Using tell() + seek() Together

f = open("sample.txt", "r")
print("Start:", f.tell())

f.read(7)
print("After reading:", f.tell())

f.seek(0)
print("Back to start:", f.tell())

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⭐ Importance of tell() and seek()

✔ Allows random access to file
✔ Helps in re-reading data
✔ Useful for large files
✔ Allows skipping unnecessary data
✔ Essential for binary file processing

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⭐ Exam-Ready Short Answer

tell() returns the current position of the file pointer in a file.
seek(offset, from_where) moves the file pointer to a specified position.
offset defines how many bytes to move, and from_where (0, 1, 2) specifies whether to move from the beginning, current position, or end of file. These methods are used for random file access and pointer control.