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Given a string that uses named placeholders for formatting, is it possible to inspect what the names are dynamically?

>>> var = '''{foo} {bar} {baz}'''
# How to do this?
>>> for k in var.inspect_named_placeholders():
>>>     print(k)
foo
bar
baz
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  • 1
    Sounds like an X-Y problem. Why do you want that? You are providing the Y, with the assumption that it is the best solution for X. Commented Sep 4, 2019 at 18:05
  • How do you intend to handle something like {foo:04d} or {foo:{bar}{baz}}? What if the user enters {0}? Commented Sep 4, 2019 at 18:07
  • 2
    Maybe you could use something like string.Formatter? Commented Sep 4, 2019 at 18:08
  • @DSM. Good find. I didn't know that would be exposed, but it makes sense, given that this is python after all. Commented Sep 4, 2019 at 18:10
  • @MadPhysicist Sorry, I do not follow. My problem is that I want to extract the named placeholders from a string. inspect_named_placeholders was not my proposed solution and was only used to show an example of something I am looking for. string.Formatter as provided by juanpa.arrivillaga and DSM is perfect. Commented Sep 4, 2019 at 18:20

1 Answer 1

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Yes, you can use the built-in parser:

>>> var = '''{foo} {bar} {baz}'''
>>> import string
>>> formatter = string.Formatter()
>>> formatter.parse(var)
<formatteriterator object at 0x109174750>
>>> list(formatter.parse(var))
[('', 'foo', '', None), (' ', 'bar', '', None), (' ', 'baz', '', None)]
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1 Comment

This is much better than using regex, thanks.

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