I am creating a program that reads a list of files from some text file and then does various things with them. I want to be able to read each line and then process it like it was typed in in a CLI. For example:
~/test1.txt -r
~/test2.txt -w "hello"
Where the flag -r saves the text in the file to some object and -w appends whatever string argument follows that flag to the file. In this case would append "hello" to test2.txt.
I know of argparse, and it does exactly what I want, but it only reads and processes commands from the command line. Is there a way to parse strings that I already have in my program like I described above?
If it cant be done with argparse, are there any other decent solutions other then coding it myself?
My guess is your want to read from a text file and treat each line as command line arguments. Here is what get you started.
import argparse
import pathlib
import shlex
# Create a parser
parser = argparse.ArgumentParser()
parser.add_argument("-r", action="store_true")
parser.add_argument("-w")
parser.add_argument("filename")
# Read the lines from the text file
data_path = pathlib.Path(__file__).with_name("input.txt")
with open(data_path, "r", encoding="utf-8") as stream:
for line in stream:
print(f"\n# {line.strip()}")
tokens = shlex.split(line)
options = parser.parse_args(tokens)
print(options)
# Do something with options
Output:
# ~/test1.txt -r
Namespace(r=True, w=None, filename='~/test1.txt')
# ~/test2.txt -w "hello"
Namespace(r=False, w='hello', filename='~/test2.txt')
Normally, we call parse.parse_args(), which parses the command-line arguments.
In order to parse a text line, we need to split that line and pass the list of tokens into parse_args.
Do not use line.split(): it does not understand quotes and escaped characters. Instead, we use shlex.split() which take care of those details.
Thank you to Charles Duffy for pointing out the ~ expansion. That can be easily fixed with the following changes:
import os
...
parser.add_argument("filename", type=os.path.expanduser)