python - How to compare all lines in some file with another line? -


i new @ python , need help.

i have file x number of lines. want compare each line of file line, , write line file if different.

i looked answer didn't find can use. tried myself doesn't work.

my code:

filename = ... my_file = open(filename, 'r+') line in my_file:     new_line = ("text")     print line     print new_line     if new_line == line:         print('same')     else:         print('diffrent')         my_file.write('%s' % (new_line))

i want application write line file if doesn't exist there.

contents of filename ==================== text text1 text2

in case above new line "text", application shouldn't because line exist in file. however, if new line "text3" should written file follows:

contents of filename ==================== text text1 text2 text3

first, let's read contents of file can check if new line in there.

existing_lines = [line.rstrip('\n') line in open(filename, 'r')]

let's have separate list named new_lines contains lines you'd check against file. can check see ones new follows:

new = [line line in new_lines if line not in existing_lines]

these lines you'd append existing file:

with open(filename, 'a') f:     [f.write(line + '\n') line in new]

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