List of variable inside a string

Question

Python provides string formatting like

s="{a}|{b}.{c}.{a}"
s.format(a=2, b=3, c=4)

which outputs

'2|3.4.2'

I'm looking for a way to get a list of "variables" inside a string.

So in my example

list_of_var(s)

should outputs

['a', 'b', 'c', 'a']

Answer 1

Using string.Formatter.parse:

>>> s = "{a}|{b}.{c}.{a}"
>>> import string
>>> formatter = string.Formatter()
>>> [item[1] for item in formatter.parse(s)]
['a', 'b', 'c', 'a']

Answer 2

You can use the regex

(?<={)\w+(?=})

Example usage

>>> import re
>>> s="{a}|{b}.{c}.{a}"
>>> re.findall(r'(?<={)\w+(?=})', s)
['a', 'b', 'c', 'a']

Regex

• (?<={) look behind, asserts the regex is presceded by {

• \w+ matches the variable name

• (?=}) look ahead asserts the regex if followed by }