Use it when it makes the most sense for a problem. Place your most specific matches first, and the most general matches last.įinally, if you have a problem that could be solved with a simple if/elif/else chain, or a dictionary lookup - use that instead! Pattern matching is powerful, but not universal. Most folks who have built lengthy if/elif/else chains will realize this, but pattern matching requires you to think about order even more carefully, due to the potential complexity. Which matches you test for first will have an impact on the efficiency and accuracy of your matching overall. The real value of structural pattern matching is being able to make matches against a pattern of objects, not just one particular object or even a selection of them.Īnother important thing to bear in mind is the order of the matches. Naive Approach: Convert the number into its binary string representation and then use a pattern matching algorithm to check the number of times the pattern has occurred in the binary representation. Simple tests against constants are fine, but if that’s all you’re doing, then a simple dictionary lookup might be a better option. Output: 1 Binary representation of 10 is 1010 and the given pattern occurs only once. The key with Python structural pattern matching is to write matches that cover the structural cases you’re trying to match against. Print (f"Unknown command '") Using Python structural pattern matching effectively It takes an object, tests the object against one or more match patterns, and takes an action if it finds a match. The match/case statement follows the same basic outline as switch/case. Structural pattern matching introduces the match/case statement and the pattern syntax to Python. Introducing Python structural pattern matching Structural pattern matching not only makes it possible to perform simple switch/case style matches, but also supports a broader range of use cases. In many cases this works well, but can be cumbersome to construct and maintain.Īfter many proposals to add a switch/case-like syntax to Python failed, a recent proposal by Python language creator Guido van Rossum and a number of other contributors has been accepted for Python 3.10: structural pattern matching. The other is to store values to match as keys in a dictionary, then use the values to take an action-e.g., store a function as a value and use the key or some other variable as input. One is to write an if/elif/else chain of expressions. The traditional ways to do this in Python aren’t elegant. In C and C++, it’s the switch/case construction in Rust, it’s called “ pattern matching.” Python, for all its power and popularity, has long lacked a form of flow control found in other languages-a way to take a value and match it elegantly against one of a number of possible conditions.
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