Parsing arguments to a python file

In summary, the forum user is seeking help with using .py scripts in CMS_SW and is having trouble declaring the file needed for the script to run. They have tried using the argparse module and have encountered an error, and are considering using C++ instead.
  • #1
magistros
4
0
Dear forum,
I would like you to help me on .py scripts.
I am using CMS_SW and I want to do something like this:

cmsRun script.py file.root

where "file.root" is the file that the .py script needs to run... But I cannot find, how I declare it to the .py code...
these .py files, are configuration files...

thank you in advance!
 
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  • #2
Try it like this:

Code:
import sys
cmd=sys.argv
filename=cmd[1]
infile = open(filename, 'r') # Now do what you want with the file
 
  • #3
Depending on the complexity of your needs, you may want to look at the argparse module.
 
  • #4
Dear phyzguy,
I tried it but I get this error
cms::Exception caught in cmsRun
---- Configuration BEGIN
FailedInputSource Configuration of primary input source has failed
---- Configuration END

Maybe the CMS_SW does not run python but something like this...

Dear jhae2.718,
I tried the argparse and it says that the argparse is missing...

Anyway, I will make it in C++..

Thank you for your time guys!
 
  • #5

Hello,

Thank you for reaching out to the forum for help with parsing arguments to a python file. It sounds like you are using CMS_SW and are trying to run a .py script with a specific file as input.

To declare the input file in your .py code, you can use the "sys" module in Python. This module allows you to access command line arguments, which is what you need to do in order to specify the input file for your script.

Here is an example of how you can use the "sys" module to parse arguments in your .py code:

import sys

input_file = sys.argv[1] # This will retrieve the first argument after the script name

# Now you can use the "input_file" variable in your code as needed
# For example:
data = open(input_file, 'r') # This will open the input file for reading

I hope this helps you to declare the input file in your .py code. Let me know if you have any further questions. Best of luck with your research!
 

What is parsing?

Parsing is the process of analyzing a string of code or text and breaking it down into its individual components or parts. In the context of a python file, parsing refers to the process of interpreting and extracting the arguments passed to the file.

Why is parsing important in python?

Parsing is important in python because it allows for the execution of a python file with specific inputs or arguments. This allows for greater flexibility and customization in the use of python scripts.

How do you parse arguments in a python file?

In python, the argparse module is commonly used for parsing arguments. This module provides a simple and efficient way to define and parse command-line arguments in a python file.

What is the difference between positional and optional arguments?

Positional arguments are required and must be specified in a specific order, while optional arguments are not required and can be specified in any order. Positional arguments are typically used for essential inputs, while optional arguments are used for more customizable inputs.

Can you provide an example of parsing arguments in a python file?

Yes, here is an example of parsing two arguments, a name and an age, in a python file using the argparse module:

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("name", help="Enter your name")
parser.add_argument("age", help="Enter your age")
args = parser.parse_args()
print("Hello " + args.name + ", you are " + args.age + " years old")

If this python file is executed with the command "python example.py John 25", the output would be "Hello John, you are 25 years old."

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