Python 3.10 pattern matching (PEP 634) - wildcard in string

I got a large list of JSON objects that I want to parse depending on the start of one of the keys, and just wildcard the rest. A lot of the keys are similar, like "matchme-foo" and "matchme-bar". There is a builtin wildcard, but it is only used for whole values, kinda like an else.

I might be overlooking something but I can't find a solution anywhere in the proposal:

Also a bit more about it in PEP-636:

My data looks like this:

data = [{
          "id"     : "matchme-foo",
          "message": "hallo this is a message",
          "id"     : "matchme-bar",
          "message": "goodbye",
          "id"     : "anotherid",
          "message": "completely diffrent event"
      }, ...]

I want to do something that can match the id without having to make a long list of |'s.

Something like this:

for event in data:
    match event:
        case {'id':'matchme-*'}: # Match all 'matchme-' no matter what comes next
        case {'id':'anotherid'}:

It's a relatively new addition to Python so there aren't many guides on how to use it yet.


  • You can use a guard.

    for event in data:
        match event:
            case {'id': x} if x.startswith("matchme"): # guard
            case {'id':'anotherid'}:

    Quoting from the official documentation:


    We can add an if clause to a pattern, known as a ā€œguardā€. If the guard is false, match goes on to try the next case block. Note that value capture happens before the guard is evaluated:

    match point:
         case Point(x, y) if x == y:
             print(f"The point is located on the diagonal Y=X at {x}.")
         case Point(x, y):
             print(f"Point is not on the diagonal.")

    See also: