Parse a nested list with python argparse

Question

Assume that I am expecting a list of lists where the inner lists have different types and lengths, e. g.,

[[1, 2], ["foo", "bar"], [3.14, "baz", 20]]

how can I parse the above list using argparse?

Most useful questions on stackoverflow:

Similar questions exist, where most useful one is here. But they are not good enough in my case as they ignore the fact that the list is nested with different data types and lenghts.

• Sam Mason: why not just do stackoverflow.com/a/24866869/1358308 but use json.loads for the type parameter?
• Meysam Sadeghi: This is what I am doing at the moment. The problem is that then you are required to parse the string, in my example "[[1, 2], ['foo', 'bar'], [3.14, 'baz', 20]]", and extract the data. Hence, I was wondering if there is a more efficient way? Could you comment how the type can be handled with json.loads?
• Sam Mason: note that using json implies that strings are in double quotes, whereas your example has single quotes. any reason for this?
• Meysam Sadeghi: No, I revised that.

Answer 1

expanding on my comment:

from argparse import ArgumentParser
import json
parser = ArgumentParser()
parser.add_argument('-l', type=json.loads)
parser.parse_args(['-l', '[[1,2],["foo","bar"],[3.14,"baz",20]]'])

prints:

Namespace(l=[[1, 2], ['foo', 'bar'], [3.14, 'baz', 20]])

• matanox: And you might need escaping the quotes when actually calling your program from bash