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Is it possible to parse a file line by line, and edit a line in-place while going through the lines?
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seek(count + cn) # place cursor at the correct character location remainder = f. read() # store all character afterwards f. seek(count + cn) # move cursor back to the correct character location f. write(text + remainder) # insert text and rewrite the remainder return # You're finished!
Is it possible to parse a file line by line, and edit a line in-place while going through the lines?
It can be simulated using a backup file as stdlib's fileinput module does.
Here's an example script that removes lines that do not satisfy some_condition from files given on the command line or stdin:
#!/usr/bin/env python # grep_some_condition.py import fileinput for line in fileinput.input(inplace=True, backup='.bak'): if some_condition(line): print line, # this goes to the current file Example:
$ python grep_some_condition.py first_file.txt second_file.txt On completion first_file.txt and second_file.txt files will contain only lines that satisfy some_condition() predicate.
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