Command Line Arguments in Python with sys.argv

Question

I want to use sys.argv to access the arguments passed to the script. Here is my code :

if __name__ == '__main__':
    data = {}
    if len(sys.argv) >= 2 :read_inputs(data, sys.argv[1])
    else : print "ERROR : the config file is required in the command line"

    if len(sys.argv) >= 3 :data['Parameters']['Mode'] = sys.argv[2]
    print_data(data)

I understand that sys.argv[1] and sys.argv[2] refer to the arguments.
My arguments are contained in a text file.

What I cannot understand is how can I tell the code that it needs to read the arguments in that exact text file. I used python Interface.py config.txt but it didn't work.

Any ideas ?

Are you expecting Python to magically guess that `argv[1]` contains a file it should go and (somehow) read to get arguments? That is **not** going to happen. — jonrsharpe, Mar 18 '15 at 10:22
You should open that file with `open()` and read data from there. What is your problem? Or you may use shell (if you working with nix-like System) to help you reading arguments like `python Interface.py $(cat config.txt)` — myaut, Mar 18 '15 at 10:22
Read that file in your code. Refer this link for the examples: http://www.tutorialspoint.com/python/python_files_io.htm — Prerak Sola, Mar 18 '15 at 10:23
So I opened the file like this : `obj = open("config.txt","r")` like it says in the link. Then I did this: `sys.argv[0] = obj.name` But it didn't work. @PrerakSola @myaut — AmyMagoria, Mar 18 '15 at 10:37
`obj.name` returns you the file name. You need to use `read()` or `readLine()` to read the contents. There are examples of it in the link I gave. Scroll down further and you'll find it. — Prerak Sola, Mar 18 '15 at 10:44

score 1 · Answer 1 · edited May 23 '17 at 11:43

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If I understand you correctly you want what would normally be on the command line to be in that file, right?

You can do that using command substitution python Interface.py $(< config.txt), as seen here

edited May 23 '17 at 11:43

Community

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answered Mar 18 '15 at 10:29

greschd

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That error should usually tell you where the syntax error is.. that's a problem in your python code. – greschd Mar 18 '15 at 10:37
It says that it's in the command : ` python Interface.py $(< config.txt) ^ SyntaxError: invalid syntax ` – AmyMagoria Mar 18 '15 at 10:39
what system are you on? – greschd Mar 18 '15 at 10:39
I meant as in what operating system... the thing I wrote works for bash shells, but not e.g. for Windows – greschd Mar 18 '15 at 10:43
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/73238/discussion-between-greschd-and-amymagoria). – greschd Mar 18 '15 at 10:44
Then I'm afraid I'm out of my area of expertise :| But I'm sure there's a similar command for Windows! – greschd Mar 18 '15 at 10:46

score 1 · Answer 2 · answered Mar 18 '15 at 12:31

Although not a direct answer to your question, I would highly recommend using the Python argparse module to parse command line argument. I your case I would add a "-c, --config" option that specifies the location of the config file that you want to use. See the documentation for examples: https://docs.python.org/3/library/argparse.html

Command Line Arguments in Python with sys.argv

2 Answers2