Two sets of arguments python

Question

I like how gdb and lldb can take two sets of arguments, one for gdb/lldb itself and one for the target application. For example:

lldb /bin/ls -- -al -foo=bar

On the left side of the double-dash '--' you can put your lldb arguments and on the right side you can put your target args. Is there a way to read two sets of arguments like this in my Python script?

well, just split the argument array: n = sys.argv.index('--'); left = sys.argv[:n]; right = sys.argv[n+1:] and catch ValueError when -- isn't found. — Jo So
– Jo So, Commented Dec 9, 2015 at 0:20
As @4ae1e1 points out, replace sys.argv with sys.argv[1:] in my comment above (best create another variable and use that) — Jo So
– Jo So, Commented Dec 9, 2015 at 0:51

Mark Ignacio · Accepted Answer · 2015-12-09 00:09:41Z

1

Yes! ArgumentParser.parse_args() can optionally take a list of arguments, formatted similarly to what you see in sys.argv.

import sys
import argparse

first_parser = argparse.ArgumentParser()
first_parser.add_argument('arg1')

second_parser = argparse.ArgumentParser()
second_parser.add_argument('arg2')

first_args = []
second_args = []
double_dashed = False
for arg in sys.argv[1:]:
    if arg == '--':
        double_dashed = True
    elif not double_dashed:
        first_args.append(arg)
    else:
        second_args.append(arg)
print(first_parser.parse_args(first_args))
print(second_parser.parse_args(second_args))

This prints out:

$ ./example.py one -- two
Namespace(arg1='one')
Namespace(arg2='two')

answered Dec 9, 2015 at 0:09

Mark Ignacio

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12 Comments

Jo So Over a year ago

@4ae1e1, appending is efficient. It takes constant averaged time (with the common double-capacity strategy). Plus, there is absolutely no need to worry about performance of argument parsing.

Jo So Over a year ago

@4ae1e1. Why do you keep claiming it is inefficient? Again, it takes constant averaged time, just like slicing.

Jo So Over a year ago

@4ae1e1: To counter your false claims

Jo So Over a year ago

And what's wrong with my comment now? Checked it and it works.

Jo So Over a year ago

Let us continue this discussion in chat.

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