Add print() option

Author: AaronDMarasco

AUTHORS.md

@@ -64,3 +64,4 @@ Authors in order of the timeline of their contributions:
 - [dtorres-sf](https://github.com/dtorres-sf) for fixing iterable moved items when iterable_compare_func is used.
 - [Florian Finkernagel](https://github.com/TyberiusPrime) for pandas and polars support.
 - Mathis Chenuet [artemisart](https://github.com/artemisart) for fixing slots classes comparison.
+- [Aaron D. Marasco](https://github.com/AaronDMarasco) added `prefix` option to `pretty()`

CHANGELOG.md

@@ -3,6 +3,7 @@
 
 - v8-0-1
     - Bugfix. Numpy should be optional.
+    - Added `prefix` option to `pretty()`
 
 - v8-0-0
 

deepdiff/serialization.py

@@ -296,7 +296,7 @@ def _to_delta_dict(self, directed=True, report_repetition_required=True, always_
 
         return deepcopy(dict(result))
 
-    def pretty(self):
+    def pretty(self, prefix=None):
         """
         The pretty human readable string output for the diff object
         regardless of what view was used to generate the diff.
@@ -310,12 +310,16 @@ def pretty(self):
             Item root[1] removed from set.
         """
         result = []
+        if prefix is None:
+            prefix = ''
         keys = sorted(self.tree.keys())  # sorting keys to guarantee constant order across python versions.
         for key in keys:
             for item_key in self.tree[key]:
                 result += [pretty_print_diff(item_key)]
 
-        return '\n'.join(result)
+        if callable(prefix):
+            return "\n".join(f"{prefix(diff=self)}{r}" for r in result)
+        return "\n".join(f"{prefix}{r}" for r in result)
 
 
 class _RestrictedUnpickler(pickle.Unpickler):

docs/view.rst

@@ -299,6 +299,29 @@ Use the pretty method for human readable output. This is regardless of what view
     Item root[4] removed from set.
     Item root[1] removed from set.
 
+The pretty method has an optional parameter ``prefix`` that allows a prefix string before every output line (*e.g.* for logging):
+    >>> from deepdiff import DeepDiff
+    >>> t1={1,2,4}
+    >>> t2={2,3}
+    >>> print(DeepDiff(t1, t2).pretty(prefix='Diff: '))
+    Diff: Item root[3] added to set.
+    Diff: Item root[4] removed from set.
+    Diff: Item root[1] removed from set.
+
+The ``prefix`` may also be a callable function. This function must accept ``**kwargs``; as of this version, the only parameter is ``diff`` but the signature allows for future expansion.
+The ``diff`` given will be the ``DeepDiff`` that ``pretty`` was called on; this allows interesting capabilities such as:
+    >>> from deepdiff import DeepDiff
+    >>> t1={1,2,4}
+    >>> t2={2,3}
+    >>> def callback(**kwargs):
+    ...     """Helper function using a hidden variable on the diff that tracks which count prints next"""
+    ...     kwargs['diff']._diff_count = 1 + getattr(kwargs['diff'], '_diff_count', 0)
+    ...     return f"Diff #{kwargs['diff']._diff_count}: "
+    ...
+    >>> print(DeepDiff(t1, t2).pretty(prefix=callback))
+    Diff #1: Item root[3] added to set.
+    Diff #2: Item root[4] removed from set.
+    Diff #3: Item root[1] removed from set.
 
 
 Text view vs. Tree view vs. vs. pretty() method

tests/test_serialization.py

@@ -330,6 +330,49 @@ def test_pretty_form_method(self, expected, verbose_level):
         result = ddiff.pretty()
         assert result == expected
 
+    @pytest.mark.parametrize("expected, verbose_level",
+                             (
+                                 ('\t\tItem root[5] added to dictionary.'
+                                  '\n\t\tItem root[3] removed from dictionary.'
+                                  '\n\t\tType of root[2] changed from int to str and value changed from 2 to "b".'
+                                  '\n\t\tValue of root[4] changed from 4 to 5.', 0),
+                                 ('\t\tItem root[5] (5) added to dictionary.'
+                                  '\n\t\tItem root[3] (3) removed from dictionary.'
+                                  '\n\t\tType of root[2] changed from int to str and value changed from 2 to "b".'
+                                  '\n\t\tValue of root[4] changed from 4 to 5.', 2),
+                             ), ids=("verbose=0", "verbose=2")
+                             )
+    def test_pretty_form_method_prefixed_simple(self, expected, verbose_level):
+        t1 = {2: 2, 3: 3, 4: 4}
+        t2 = {2: 'b', 4: 5, 5: 5}
+        ddiff = DeepDiff(t1, t2, verbose_level=verbose_level)
+        result = ddiff.pretty(prefix="\t\t")
+        assert result == expected
+
+    @pytest.mark.parametrize("expected, verbose_level",
+                             (
+                                 ('Diff #1: Item root[5] added to dictionary.'
+                                  '\nDiff #2: Item root[3] removed from dictionary.'
+                                  '\nDiff #3: Type of root[2] changed from int to str and value changed from 2 to "b".'
+                                  '\nDiff #4: Value of root[4] changed from 4 to 5.', 0),
+                                 ('Diff #1: Item root[5] (5) added to dictionary.'
+                                  '\nDiff #2: Item root[3] (3) removed from dictionary.'
+                                  '\nDiff #3: Type of root[2] changed from int to str and value changed from 2 to "b".'
+                                  '\nDiff #4: Value of root[4] changed from 4 to 5.', 2),
+                             ), ids=("verbose=0", "verbose=2")
+                             )
+    def test_pretty_form_method_prefixed_callback(self, expected, verbose_level):
+        def prefix_callback(**kwargs):
+            """Helper function using a hidden variable on the diff that tracks which count prints next"""
+            kwargs['diff']._diff_count = 1 + getattr(kwargs['diff'], '_diff_count', 0)
+            return f"Diff #{kwargs['diff']._diff_count}: "
+
+        t1 = {2: 2, 3: 3, 4: 4}
+        t2 = {2: 'b', 4: 5, 5: 5}
+        ddiff = DeepDiff(t1, t2, verbose_level=verbose_level)
+        result = ddiff.pretty(prefix=prefix_callback)
+        assert result == expected
+
     @pytest.mark.parametrize('test_num, value, func_to_convert_back', [
         (1, {'10': None}, None),
         (2, {"type_changes": {"root": {"old_type": None, "new_type": list, "new_value": ["你好", 2, 3, 5]}}}, None),