https://github.com/aronhoff/regex_spm

Enable Structural Pattern Matching for Python regular expressions
https://github.com/aronhoff/regex_spm

Last synced: about 1 month ago
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Enable Structural Pattern Matching for Python regular expressions

• Host: GitHub
• URL: https://github.com/aronhoff/regex_spm
• Owner: aronhoff
• License: mit
• Created: 2022-06-17T07:38:51.000Z (over 2 years ago)
• Default Branch: main
• Last Pushed: 2024-07-04T17:19:53.000Z (5 months ago)
• Last Synced: 2024-10-30T11:50:51.501Z (about 1 month ago)
• Language: Python
• Size: 8.79 KB
• Stars: 19
• Watchers: 3
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# regex_spm

Enable Structural Pattern Matching ([PEP-634](https://peps.python.org/pep-0634/)) for Python 

regular expressions

The string goes in the place of the subject, wrapped by a `regex_spm` function.


The various possible regex patterns go after the `case`s.

### Simple example

```python

import regex_spm

match regex_spm.fullmatch_in("abracadabra"):

  case r"\d+": print("It's all digits")

  case r"\D+": print("There are no digits in the search string")

  case _: print("It's something else")

```

`regex_spm` provides 3 functions, which correspond to `re` search functions:

- `re.search` → `regex_spm.search_in`

- `re.match` → `regex_spm.match_in`

- `re.fullmatch` → `regex_spm.fullmatch_in`

### Accessing the match object

To access the matched groups or the entire `re.Match` object, simply capture the pattern:

```python

match regex_spm.fullmatch_in("123,45"):

  case r"(\d+),(?P\d+)" as m:

    print("Notice the `as m` at the end of the line above")

    print(f"The first group is {m[1]}")

    print(f"The second group is {m['second']}")

    print(f"The full `re.Match` object is available as {m.match}")

```

### Pattern caveats (workaround below)

**#1:** Due to the mechanics of Python SPM, it is not possible to use case blocks like `case 

re.compile(r"my-regex"): ...`. Python would try to use `re.compile` as a class name, which does not

exist.

**#2:** It is also not possible to save patterns to simple local variables like:

```python

pattern1 = r"my-first-pattern"

pattern2 = re.compile(r"my-second-pattern")

match regex_spm.search_in(my_string):

  case pattern1: print("This does not work, it matches any string. Python interprets `pattern1` "

                       "as simply a new capture variable name, hiding its previous value.")

  case pattern2: print("This does not work either")

```

### Using patterns from variables (caveat workaround)

Python requires "value patterns" to use a "dotted name", i.e. there must be a `.` in tha name used 

to reach the stored pattern. 

Putting stored patterns in a class like below is sufficient.

```python

class PageRegexes:

  index = re.compile(r"example\.com/index.html")

  shopping_cart = r"example\.com/shopping_cart.html"

match regex_spm.search_in(my_url):

  case PageRegexes.index: print("It's the index page")

  case PageRegexes.shopping_cart: print("It's the shopping cart page")

  case r"example\.com/about.html": print("You can even mix and match")

```

## Install

Requires Python 3.10+ of course

```bash

pip install regex_spm

```