Python 3 - File seek() Method

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Description

The method seek() sets the file's current position at the offset. The whence argument is optional and defaults to 0, which means absolute file positioning, other values are 1 which means seek relative to the current position and 2 means seek relative to the file's end.

There is no return value. Note that if the file is opened for appending using either 'a' or 'a+', any seek() operations will be undone at the next write.

If the file is only opened for writing in append mode using 'a', this method is essentially a no-op, but it remains useful for files opened in append mode with reading enabled (mode 'a+').

If the file is opened in text mode using 't', only offsets returned by tell() are legal. Use of other offsets causes undefined behavior.

Note that not all file objects are seekable.

Syntax

Following is the syntax for seek() method −

fileObject.seek(offset[, whence])

Parameters

• offset − This is the position of the read/write pointer within the file.

• whence − This is optional and defaults to 0 which means absolute file positioning, other values are 1 which means seek relative to the current position and 2 means seek relative to the file's end.

Return Value

This method does not return any value.

Example

The following example shows the usage of seek() method.

Assuming that 'foo.txt' file contains following text:
This is 1st line
This is 2nd line
This is 3rd line
This is 4th line
This is 5th line

#!/usr/bin/python3

# Open a file
fo = open("foo.txt", "r+")
print ("Name of the file: ", fo.name)

line = fo.readlines()
print ("Read Line: %s" % (line))

# Again set the pointer to the beginning
fo.seek(0, 0)
line = fo.readline()
print ("Read Line: %s" % (line))

# Close opened file
fo.close()

Result

When we run the above program, it produces the following result −

Name of the file:  foo.txt
Read Line: ['This is 1st line\n', 'This is 2nd line\n', 'This is 3rd line\n', 'This is 4th line\n', 'This is 5th line']
Read Line: This is 1st line