Menu
I just found the pattern matching feature in Racket very powerful.
> (match '(1 2 3) [(list a b c) (list c b a)])
'(3 2 1)
> (match '(1 2 3) [(list 1 a ...) a])
'(2 3)
> (match '(1 2 3)
[(list 1 a ..3) a]
[_ 'else])
'else
> (match '(1 2 3 4)
[(list 1 a ..3) a]
[_ 'else])
'(2 3 4)
> (match '(1 2 3 4 5)
[(list 1 a ..3 5) a]
[_ 'else])
'(2 3 4)
> (match '(1 (2) (2) (2) 5)
[(list 1 (list a) ..3 5) a]
[_ 'else])
'(2 2 2)
Is there similar syntax sugar or library to do that in Python?
732
'Structural Pattern Matching' was newly introduced in Python 3.10. The syntax for this new feature was proposed in PEP 622 in JUne 2020. The pattern matching statement of Python was inspired by similar syntax found in Scala, Erlang, and other languages.
regex = r"([a-zA-Z]+) (\d+)" if re.search(regex, "Jan 2"): match = re.search(regex, "Jan 2") # This will print [0, 5), since it matches at the beginning and end of the # string print("Match at index %s, %s" % (match. start(), match. end())) # The groups contain the matched values. In particular: # match.
As of early 2021, the match keyword does not exist in the released Python versions <= 3.9. Since Python doesn't have any functionality similar to switch/case in other languages, you'd typically use nested if/elif/else statements or a dictionary.
Use re. match() to check if a string matches a pattern A pattern specifies a sequence of characters that can be matched to a string and follows the regular expression syntax in Python. re. match(pattern, string) tests if the regex pattern matches string .
No there is not, python's pattern matching is only iterable unpacking like this:
>>> (x, y) = (1, 2)
>>> print x, y
1 2
Or in function definition:
>>> def x((x, y)):
...
Or in python 3:
>>> x, *y = (1, 2, 3)
>>> print(x)
1
>>> print(y)
[2, 3]
But there are some of external libraries that realize pattern matching.
175
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
