I am using two test scripts to teach myself how to use argparse and subprocess libraries in Python. I am confused about the type=int value in add_argument().
calculator.py:
import sys
x = int(sys.argv[1])
y = int(sys.argv[2])
print(x,y)
print(x+y)
wrapper.py:
from subprocess import run
import argparse
import sys
parser = argparse.ArgumentParser(description='Wrapper.')
parser.add_argument('-x', nargs=1, type=int, dest='x', default=0, help='x.', required=True)
parser.add_argument('-y', nargs=1, type=int, dest='y', default=0, help='y.', required=True)
args = parser.parse_args()
if len(sys.argv) == 1:
parser.print_help()
else:
print('args.x and args.y')
run(["python","calculator.py", str(args.x), str(args.y)])
print('args.x[0] and args.y[0]')
run(["python","calculator.py", str(args.x[0]), str(args.y[0])])
Output:
args.x and args.y
[1] [8]
[1][8]
args.x[0] and args.y[0]
1 8
9
To me the above is unexpected behaviour. I want the values of args.x and args.y to be ints, but they are lists with a single entry. Can someone explain why this is and possibly how to change my add_argument lines to store ints and/or demonstrate proper usage of argparse?
This question:Python argparse: default argument stored as string, not list was flagged as similar. Although the solution is the same, the question is not - there the question was about the default value not being a list, here the stored value is a list. In that question the title does not ask the same question as the body, therefore I did not realise I could use the answer to that question. I have submitted an answer to that question elaborating on this point.
Remove the nargs=1 part.
From: https://docs.python.org/3/library/argparse.html#nargs
Note that nargs=1 produces a list of one item. This is different from the default, in which the item is produced by itself.