Continue reading file from the position where it was left

Question

I have to read a file multiple times in which some error info is appended everyday. Is there a way to start reading the file from the point it was left previous day instead of start reading from beginning again? I don't have permission to write in file. so marking the end is out of option. One possible way i got is to store the cursor position and then seek to that position next time.. Is there any other way through python?

Answer 1

You can use the python tell file method to see what position you are in a file before you close it and the seek method to return to that position after you open it again.

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Example:

Given a file foo with the contents

edas
agfa
agf
fgfgfg

You can return to a given position as follows:

>>> f = open('foo')
>>> f.tell()
0
>>> f.readline()
'edas\n'
>>> f.tell()
5
>>> f.close()
>>> f = open('foo')
>>> f.tell()
0
>>> f.seek(5)
>>> f.readline()
'agfa\n'