python match case part of a string

Question

I want to know if I can use match cases within Python to match within a string - that is, if a string contains the match case. Example:

mystring = "xmas holidays"
match mystring:
      case "holidays":
           return true
      case "workday":
           return false

I can see why it wouldn't, since this could potentially match several cases at once, but I wanted to know if it was possible.

Answer 1

You could use the [*_] wildcard sequence capture pattern: https://peps.python.org/pep-0622/#sequence-patterns

def is_holiday(yourstring: str):
    match yourstring.split():
        case [*_, "holidays"]:
            return True
        case [*_, "workday"]:
            return False


print(is_holiday("xmas holidays"))

Answer 2

In match statement, strings are compared using == operator which means that case patterns must be exactly equal to the match expression(mystring in this case) .

In order to solve this problem you can create a custom class which inherit from str and overrides the __eq__ method. This method should delegate to __contains__.

>>> class MyStr(str):
...     def __eq__(self, other):
...             return self.__contains__(other)
... 
>>> 
>>> mystring = MyStr("xmas holidays")
>>> match mystring:
...     case "holiday":
...             print("I am here...")
... 
I am here...

Answer 3

You can simply use the guard feature along with capture:

>>>my_str = "iwill/predict_something"
>>>match my_str:
...    case str(x) if 'predict' in x:
...        print("match!")
...    case _:
...        print("nah, dog")
...
match!