Wrong python unified_diff output

Question

I'm trying to get json diff using difflib.unified_diff but the out seems to be wrong.

from difflib import unified_diff
import sys

sone = """
{
    "one": 1,
    "a": "A",
    "b": "B"
}
    """

stwo = """
{
    "two": 2,
    "a": "A",
    "b": "B"
}
    """

for line in unified_diff(sone, stwo, fromfile="one", tofile="two", lineterm='\n'):
    sys.stdout.write(line)

And the output looks like below,

--- one
+++ two
@@ -6,13 +6,13 @@
     "+t+w o-n-e " :  -1+2

Where I should be getting something like below,

@@ -1,5 +1,5 @@
 {
-    "one": 1,
+    "two": 2,
     "a": "A",
     "b": "B"
 }

I'm using Python 2.7.14 :: Anaconda custom (64-bit) I think I'm doing something silly

Answer 1

The output is correct. The first two inputs to unified_diff are normally iterators of strings, as if you read in from fp.readlines() .

Because you only give a single sting, it is treating it as if it is the only string from the iterator. In other words, it is treating it as one long string (which it is), and not a separate lines from a file.

To get the output your expect, you need to split the multiline strings on the linebreak.

for line in unified_diff(sone.split('\n'), stwo.split('\n')):
    print(line)