python sys.argv differentiate int and string

Question

Simply put, how can I differentiate these two in test.py:

python test.py 1
python test.py '1'

Workaround is OK.

Edit:

This workaround looks cool but too complex: argparse
Let the invoker specify args later, in python code use arg = input('Please enter either an integer or a string')
And other workarounds as presented in the answers of this question.

Thank you all for the replies. Every body +1.

And something like optparse isn't an option, yeah? docs.python.org/library/optparse.html#standard-option-types — billinkc
– billinkc, Commented Aug 13, 2011 at 14:18
Would you consider making the first argument a format string? Something like "ssiiss" could let your python script know to expect two strings, followed by two integers, followed by two strings. — ajwood
– ajwood, Commented Aug 13, 2011 at 14:31
you must be joking calling standard lib, made exactly for such sort of tasks, a 'workaround'. — Roman Bodnarchuk
– Roman Bodnarchuk, Commented Aug 13, 2011 at 14:50
@Roman Bodnarchuk, I don't think argparse can solve the original problem as every body said it is impossible. Can it? So I call it a workaround. — Tyler Liu
– Tyler Liu, Commented Aug 13, 2011 at 14:58

ajwood · Accepted Answer · 2011-08-13 14:09:35Z

4

The quotes are consumed by the shell. If you want to get them into python, you'll have to invoke like python test.py 1 "'2'" "'3'" 4

answered Aug 13, 2011 at 14:09

ajwood

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3 Comments

Tyler Liu Over a year ago

The invoker of the python file is not me and I can't tell them to do that. They prefer 1 '2' '3' 4 and I have to differentiate those with quotes and those without quotes in python code

Rosh Oxymoron Over a year ago

It's not possible to differentiate them. The quotes are shell syntax and is in no way part of how arguments are passed. Command line arguments are always strings and don't require/include quoting and escaping when on their own.

Manuel Leuenberger Over a year ago

@Tyler Long: This is not possible. As ajwood said, " and ' are consumed by the shell. The Python interpreter will always get 1 2 3 4 as strings, no matter if they had quotes or not in the shell.

Roman Bodnarchuk · Accepted Answer · 2011-08-13 14:28:14Z

3

It is common handling of args, performed by shell. " and ' are ignored, since you may use them to pass, for instance, few words as one argument.

This means that you can't differentiate '1' and 1 in Python.

edited Aug 13, 2011 at 14:28

answered Aug 13, 2011 at 14:07

Roman Bodnarchuk

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3 Comments

Tyler Liu Over a year ago

But you didn't answer my question: how to differentiate those with quotes and those without quotes in python code?

hamstergene Over a year ago

There is no way. Quotes are handled by shell, Python doesn't see them.

Tyler Liu Over a year ago

At least there is a way for windows. See Eugene Homyakov's answer

Rosh Oxymoron · Accepted Answer · 2011-08-13 14:35:11Z

The shell command line doesn't support passing arguments of different types. If you want to have commands with arguments of different types you need to write your own command line or at least your own command parser.

Variant 1:

Usage:python test.py "1 2 '3' '4'"

Implementation:

command = sys.argv[1]
arguments = map(ast.literal_eval, command.split())
print arguments

Variant 2:

Usage:

python test.py
1 2 '3' 4'
5 6 '7' 8'

Implementation:

for line in sys.stdin:
    arguments = map(ast.literal_eval, line.split())
    print arguments

(Of course, you'd probably want to use raw_input to read the command lines, and readline when it is available, that's merely an example.)

A much better solution would be to actually know what kind of arguments you're expected to get and parse them as such, preferably by using a module like argparse.

hamstergene · Accepted Answer · 2011-08-13 14:44:45Z

2

Windows-specific:

# test.py
import win32api
print(win32api.GetCommandLine())

Example:

D:\>python3 test.py 3 "4"
C:\Python32\python3.EXE  test.py 3 "4"

You can then parse the command line yourself.

answered Aug 13, 2011 at 14:44

hamstergene

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1 Comment

Tyler Liu Over a year ago

If I could accept more than one answers, yours is definitely among them. Thank you.

Ned Batchelder · Accepted Answer · 2011-08-13 14:17:13Z

1

As you can see from your experiment, the quotes are gone by the time Python is invoked. You'll have to change how the Python is invoked.

answered Aug 13, 2011 at 14:17

Ned Batchelder

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2 Comments

Tyler Liu Over a year ago

Sadly it is almost impossible as I can't change the habit of the invokers.

Rosh Oxymoron Over a year ago

How did they get a habit to do something that is not possible? Where did they gain it, because it can't be the shell? Have you considered writing your own command line?

vikram360 · Accepted Answer · 2011-08-15 12:04:55Z

0

I'm not sure how correct I am, but if you're using only integer command line arguments, you can typecast it to be int.

suppose (in *nix), I run my program as:

./test.py 1

I can in my program say something line

import sys
def main():
  a=int(sys.argv[1])

answered Aug 15, 2011 at 12:04

vikram360

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