Compare two files report difference in python

Question

I have 2 files called  hosts   in different directories   I want to compare them using python to see if they are IDENTICAL  If they are not Identical  I want to print the difference on the screen    So far I have tried this  hosts0   open dst1     hosts   r    hosts1   open dst2     hosts   r    lines1   hosts0 readlines    for i lines2 in enumerate hosts1       if lines2    lines1 i           print  line    i    in hosts1 is different  n          print lines2     else          print  same    But when I run this  I get   File    audit py   line 34  in  lt module gt    if lines2    lines1 i   IndexError  list index out of range   Which means one of the hosts has more lines than the other   Is there a better method to compare 2 files and report the difference

User · Answer

hosts0   open  C path  a txt   r   hosts1   open  C path  b txt   r    lines1   hosts0 readlines    for i lines2 in enumerate hosts1       if lines2    lines1 i           print  line    i    in hosts1 is different  n          print lines2     else          print  same    The above code is working for me  Can you please indicate what error you are facing

User · Answer

You can add an conditional statement  If your array goes beyond index  then break and print the rest of the file

User · Answer

The difflib library is useful for this  and comes in the standard library  I like the unified diff format   http   docs python org 2 library difflib html difflib unified diff  import difflib import sys  with open   tmp hosts0    r   as hosts0      with open   tmp hosts1    r   as hosts1          diff   difflib unified diff              hosts0 readlines                hosts1 readlines                fromfile  hosts0               tofile  hosts1                     for line in diff              sys stdout write line    Outputs   --- hosts0     hosts1    -1 5  1 4     one  two -dogs  three   And here is a dodgy version that ignores certain lines  There might be edge cases that don t work  and there are surely better ways to do this  but maybe it will be good enough for your purposes   import difflib import sys  with open   tmp hosts0    r   as hosts0      with open   tmp hosts1    r   as hosts1          diff   difflib unified diff              hosts0 readlines                hosts1 readlines                fromfile  hosts0               tofile  hosts1               n 0                    for line in diff              for prefix in   ---                                 if line startswith prefix                       break             else                  sys stdout write line 1

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import difflib  lines1       dog cat bird buffalo gophers hound horse     strip   splitlines    lines2       cat dog bird buffalo gopher horse mouse     strip   splitlines      Changes    swapped positions of cat and dog   changed gophers to gopher   removed hound   added mouse  for line in difflib unified diff lines1  lines2  fromfile  file1   tofile  file2   lineterm          print line   Outputs the following   --- file1     file2    -1 7  1 7     cat  dog -cat  bird  buffalo -gophers -hound  gopher  horse  mouse   This diff gives you context -- surrounding lines to help make it clear how the file is different  You can see  cat  here twice  because it was removed from below  dog  and added above it   You can use n 0 to remove the context   for line in difflib unified diff lines1  lines2  fromfile  file1   tofile  file2   lineterm     n 0       print line   Outputting this   --- file1     file2    -0 0  1     cat    -2  2 0    -cat    -5 2  5    -gophers -hound  gopher    -7 0  7     mouse   But now it s full of the      lines telling you the position in the file that has changed  Let s remove the extra lines to make it more readable   for line in difflib unified diff lines1  lines2  fromfile  file1   tofile  file2   lineterm     n 0       for prefix in   ---                         if line startswith prefix               break     else          print line   Giving us this output    cat -cat -gophers -hound  gopher  mouse   Now what do you want it to do  If you ignore all removed lines  then you won t see that  hound  was removed  If you re happy just showing the additions to the file  then you could do this   diff   difflib unified diff lines1  lines2  fromfile  file1   tofile  file2   lineterm     n 0  lines   list diff  2   added    line 1   for line in lines if line 0          removed    line 1   for line in lines if line 0      -    print  additions   for line in added      print line print print  additions  ignoring position  for line in added      if line not in removed          print line   Outputting   additions  cat gopher mouse  additions  ignoring position  gopher mouse   You can probably tell by now that there are various ways to  print the differences  of two files  so you will need to be very specific if you want more help

User · Answer

import difflib f open  a txt   r     open a file f1 open  b txt   r    open another file to compare str1 f read   str2 f1 read   str1 str1 split     split the words in file by default through the spce str2 str2 split   d difflib Differ         compare and just print diff list d compare str2 str1   print   n  join diff

[python] Compare two files report difference in python

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