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Question:
How to use Python pattern matching to match class types?

Summary: 

In Python, you can use pattern matching (also known as structural pattern matching or match statement) introduced in Python 3.10 to match class types. Pattern matching allows you to write more concise and readable code for conditional branching based on the structure of data. 


Solution:

You can use the below code to match class type in Python

class Tree:

    def __init__(self, name):

        self.kind = name

    

def what_is(t):

    match t:

        case Tree(kind="oak"):

            return "oak"

        case Tree():

            return "tree"

        case _:

            return "shrug"


print(what_is(Tree(name="oak")))    # oak

print(what_is(Tree(name="birch")))  # tree

print(what_is(17))                  # shrug


TypeError: Tree.__init__() got an unexpected keyword argument 'kind'


match Tree:

    case type(__init__=initializer):

        print("Tree is a type, and this is its initializer:")

        print(initializer)


# => Tree is a type, and this is its initializer:

#    <function Tree.__init__ at 0x1098593a0>


Explanation:

Here's what each case does:


  • case Tree(kind="oak"):: Matches instances of Tree with kind attribute set to "oak".

  • case Tree():: Matches any instance of Tree regardless of its kind attribute.

  • case _:: Matches any other input that doesn't match the above cases.


Answered by: >Amadan

Credit: >Stackoverflow


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