listdiffer

List Differ

Version: 0.2.0

Description

Calculates longest common sequence on text, lists of numbers or characters, or lists of objects.

When comparing objects, make sure that the objects are hashable, i.e. override the __hash()__ method of the class. It is also a good idea to override the __eq()__ method if you have some custom logic for comparing items. This could be the case if your business logic considers close values as similar.

If you want to compare two strings ignoring casing, then simply call lower on each string before passing as argument.

Patch String Generation

The format_diff_text_as_patch, or the companion format_diff_as_patch, function can be used to generate a patch string from the diff result.

The patch string can be used to patch the first string to the second string. It can also be persisted and used later to patch the original string, thereby serving as a change log.

The patch string can be read back to a List[Delta[str]] using the parse_patch_text function in the patch_parser module.

Examples

Example 1 - Strings

Calculate a diff between two strings

Same strings

from listdiffer import differ

first = 'string'
second = 'string'
diff = differ.diff_text(first, second, False, False)

assert len(diff) == 0

Different strings

from listdiffer import differ

first = 'first string'
second = 'second string'
diff = differ.diff_text(first, second, False, False)

assert len(diff) == 1

Example 2 - List of integers

Calculate a diff between two strings

Same lists

from listdiffer import differ

first = [1, 2, 3]
second = [1, 2, 3]
d = differ.diff(first, second)

assert len(d) == 0

Different lists

from listdiffer import differ

first = [1, 2, 3]
second = [1, 2, 4]
d = differ.diff(first, second)

assert len(d) == 1

Example 3 - Lists of objects

Same lists

from listdiffer import differ

@dataclass
class TestItem:
    text: str
    value: int

    def __eq__(self, other):
        return self.text == other.text and self.value == other.value

    def __hash__(self):
        return hash((self.text, self.value))

source = [TestItem('test', 1), TestItem('test', 2), TestItem('test', 3)]
compare = [TestItem('test', 1), TestItem('test', 2), TestItem('test', 3)]
result = differ.diff(source, compare)

assert len(result) == 0

Different lists

from listdiffer import differ

@dataclass
class TestItem:
    text: str
    value: int

    def __eq__(self, other):
        return self.text == other.text and self.value == other.value

    def __hash__(self):
        return hash((self.text, self.value))

source = [TestItem('test', 1), TestItem('test', 2), TestItem('test', 3)]
compare = [TestItem('test', 1), TestItem('test', 2), TestItem('test', 3), TestItem('test', 4)]
result = differ.diff(source, compare)

assert len(result) == 1

Example 4 - Patch string generation

```python

text1 = """line1 line2 line3""" text2 = """line1 line2 lineX"""

    patch = format_diff_text_as_patch(text1, text2)

    assert """diff

@@ -2,1 +2,1 @@ line1 line2

• lineX

• line3 """ == patch