Count number of placeholders in a `str.format` template

count_n_placeholders_strformat.py

import string

# Reference: https://stackoverflow.com/a/46161774/7881370
# Access date: 2019-03-23
def count_n_placeholders(template: str) -> int:
    return sum(1 for _ in filter(lambda x: x[1] is not None,
                                 string.Formatter().parse(template)))