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seek(), tell() and other functions

 


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seek(), tell() and Other Functions in Python

Python provides several functions to manipulate the file pointer while reading or writing files. Here are some commonly used functions:

1. seek()

The seek() method sets the file's current position at the offset. The position is calculated from the beginning of the file, unless the optional whence parameter is provided. The whence parameter can take the following values:

  • 0: default, the beginning of the file
  • 1: current file position
  • 2: end of the file

# Open the file in read mode
with open('example.txt', 'r') as file:
    # Move the file pointer to the beginning of the file
    file.seek(0)
    
    # Read the first 10 characters
    content = file.read(10)
    print(content)

2. tell()

The tell() method returns the current position of the file pointer within the file.


# Open the file in read mode
with open('example.txt', 'r') as file:
    # Read the first 10 characters
    content = file.read(10)
    print(content)
    
    # Get the current position of the file pointer
    position = file.tell()
    print(position)

3. truncate()

The truncate() method resizes the file to the given number of bytes. If the size is not specified, it resizes the file to the current file pointer position.


# Open the file in write mode
with open('example.txt', 'w') as file:
    # Write some content to the file
    file.write('Hello, World!')
    
    # Resize the file to the first 5 bytes
    file.truncate(5)

4. flush()

The flush() method flushes the internal buffer, ensuring that all data is written to the file.


# Open the file in write mode
with open('example.txt', 'w') as file:
    # Write some content to the file
    file.write('Hello, World!')
    
    # Flush the internal buffer
    file.flush()

5. fileno()

The fileno() method returns the file descriptor, which is a unique integer handle assigned to the file by the operating system.


# Open the file in read mode
with open('example.txt', 'r') as file:
    # Get the file descriptor
    file_descriptor = file.fileno()
    print(file_descriptor)
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