Give an optional CLI count a typed default
Also published in our Blogger archive.
An optional count often needs a useful value whether or not a caller writes the option. type=int converts a supplied command-line token, while default=3 supplies an integer directly when --count is absent. The example parses two synthetic invocations: the first models an omitted option and produces 3; the second models --count 5 and produces 5. The assertions verify the values and confirm that both results are int instances before arithmetic uses them.
Using an integer object as the default matters: a string default such as "3" can make downstream type expectations less obvious. type=int will reject non-integer textual input through argparse's normal error path, but it does not impose business rules such as a positive upper bound. Add choices, a custom converter, or post-parse validation if zero, negatives, or excessively large counts are invalid for the application. The output prints both parse results rather than claiming a real shell invocation occurred.
argparse is standard library functionality available from Python 3.2. Its official documentation describes default, and the type section describes conversion of command-line values.
AI assistance disclosure: this article was drafted with AI assistance and should be checked in its target CLI context.
import argparse
parser = argparse.ArgumentParser(prog="repeat")
parser.add_argument("--count", type=int, default=3)
default_args = parser.parse_args([])
provided_args = parser.parse_args(["--count", "5"])
assert default_args.count == 3
assert provided_args.count == 5
assert isinstance(default_args.count, int)
assert isinstance(provided_args.count, int)
print(f"default={default_args.count}")
print(f"provided={provided_args.count}")default=3
provided=5