# Python Difflib Module

The `difflib` module provides classes and functions for comparing sequences. It can be used for example, for comparing files, and can produce difference information in various formats, including HTML and context and unified diffs.

## Importing the Module

```python
import difflib
```

## Comparing Sequences

### `SequenceMatcher`

This is a flexible class for comparing pairs of sequences of any type, so long as the sequence elements are hashable.

```python
import difflib

s1 = "Apple"
s2 = "Appel"

matcher = difflib.SequenceMatcher(None, s1, s2)
print(f"Ratio: {matcher.ratio()}") # Output: 0.8
```

You can also get detailed opcodes describing how to turn `s1` into `s2`.

```python
for tag, i1, i2, j1, j2 in matcher.get_opcodes():
    print(f"{tag:7} a[{i1}:{i2}] ({s1[i1:i2]}) b[{j1}:{j2}] ({s2[j1:j2]})")
```

## Finding Close Matches

The `get_close_matches()` function returns a list of the best "good enough" matches.

```python
import difflib

words = ['apple', 'ape', 'application', 'peach', 'puppy']
matches = difflib.get_close_matches('appel', words)

print(matches)
# Output: ['apple', 'ape']
```

## Generating Diffs

### `Differ`

The `Differ` class is used for comparing sequences of lines of text, and producing human-readable differences or deltas.

```python
import difflib

text1 = """line 1
line 2
line 3""".splitlines(keepends=True)

text2 = """line 1
line 2 changed
line 3""".splitlines(keepends=True)

d = difflib.Differ()
diff = d.compare(text1, text2)

print(''.join(diff))
```

### `unified_diff`

For a more compact diff (like the `diff` command line tool), use `unified_diff()`.

```python
import difflib

diff = difflib.unified_diff(text1, text2, fromfile='file1', tofile='file2')
print(''.join(diff))
```

### `HtmlDiff`

This class can be used to create an HTML table (or a complete HTML file) showing a side by side, line by line comparison of text with inter-line and intra-line change highlights.

```python
import difflib

d = difflib.HtmlDiff()
html = d.make_file(text1, text2)

# with open('diff.html', 'w') as f:
#     f.write(html)
```

[[programming/python/python]]