{"id":696,"date":"2019-09-11T12:18:59","date_gmt":"2019-09-11T12:18:59","guid":{"rendered":"https:\/\/www.askpython.com\/?p=696"},"modified":"2019-12-16T05:01:39","modified_gmt":"2019-12-16T05:01:39","slug":"python-command-line-arguments","status":"publish","type":"post","link":"https:\/\/www.askpython.com\/python\/python-command-line-arguments","title":{"rendered":"Python Command Line Arguments – 3 Ways to Read\/Parse"},"content":{"rendered":"\n

Python command-line arguments are the parameters provided to the script while executing it. The command-line arguments are used to provide specific inputs to the program. <\/p>\n\n\n\n

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What is the benefit of Python Command Line Arguments?<\/h2>\n\n\n\n

Python command-line arguments help us to keep our program generic in nature. For example, we can write a program to process a CSV file. If we pass the CSV file name from the command-line, then our program will work for any CSV file. This will make our program loosely coupled and it will be easy to maintain it.<\/p>\n\n\n\n

Another benefit of command-line arguments is the additional security that comes with it. Let’s say we have a program to save data into the database. If we store the database credentials in the script or some configuration file, it can be accessed and executed by anyone having access to the files. But, if the user\/password is provided as a command-line argument, then it’s not present in the file system and our program is more secured.<\/p>\n\n\n\n

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How to Pass Command-line Arguments in Python?<\/h2>\n\n\n\n

If you are running the python script from the terminal, just pass the arguments after the script name. The arguments are separated with white space characters.<\/p>\n\n\n

\n$ python script.py arg1 arg2 ... argN\n<\/pre><\/div>\n\n\n
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Passing Command-line arguments in PyCharm<\/h2>\n\n\n\n
PyCharm is the most popular IDE for Python programming. If you want to pass command-line arguments to a python program, go to “Run > Edit Configurations” and set the Parameters value and save it.<\/p>\n\n\n\n
\"Python
Python Command Line Arguments PyCharm<\/figcaption><\/figure><\/div>\n\n\n\n
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How to Read Command-line arguments in Python Script?<\/h2>\n\n\n\n
There are three popular modules to read and parse command-line arguments in the Python script.<\/p>\n\n\n\n
  1. sys.argv<\/li>
  2. getopt<\/li>
  3. argparse<\/li><\/ol>\n\n\n\n
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    1. Reading Python Command-line arguments using the sys module<\/h2>\n\n\n\n
    The command-line arguments are stored in the sys module argv<\/code> variable, which is a list<\/a> of strings. We can read the command-line arguments from this list and use it in our program.<\/p>\n\n\n\n
    Note that the script name is also part of the command-line arguments in the sys.argv<\/code> variable.<\/p>\n\n\n
    \nimport sys\n\nif len(sys.argv) != 2:\n    raise ValueError('Please provide email-id to send the email.')\n\nprint(f'Script Name is {sys.argv[0]}')\n\nemail = sys.argv[1]\n\nprint(f'Sending test email to {email}')\n<\/pre><\/div>\n\n\n
    Output:<\/strong><\/p>\n\n\n
    \n$ python3.7 command-line-args.py test@askpython.com\nScript Name is command-line-args.py\nSending test email to test@askpython.com\n$ python3.7 command-line-args.py                   \nTraceback (most recent call last):\n  File "command-line-args.py", line 4, in <module>\n    raise ValueError('Please provide email-id to send the email.')\nValueError: Please provide email-id to send the email.\n$\n<\/pre><\/div>\n\n\n
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    2. Parsing Command-line arguments using the getopt module<\/h2>\n\n\n\n
    Python getopt module works in a similar way as the Unix getopt() function. This module is helpful when you want the script to accept options and their values, similar to the many Unix commands.<\/p>\n\n\n\n
    This module works in conjunction with the sys.argv to parse the command-line arguments and extract the options values in a list of tuples<\/a>.<\/p>\n\n\n
    \nimport getopt\nimport sys\n\nargv = sys.argv[1:]\n\nopts, args = getopt.getopt(argv, 'x:y:')\n\n# list of options tuple (opt, value)\nprint(f'Options Tuple is {opts}')\n\n# list of remaining command-line arguments\nprint(f'Additional Command-line arguments list is {args}')\n<\/pre><\/div>\n\n\n
    Output:<\/strong><\/p>\n\n\n
    \n$ python3.7 command-line-args.py -x 1 -y 2 A B            \nOptions Tuple is [('-x', '1'), ('-y', '2')]\nAdditional Command-line arguments list is ['A', 'B']\n$ \n<\/pre><\/div>\n\n\n
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    3. Parsing Command-line arguments using argparse module<\/h2>\n\n\n\n
    We can use Python argparse module also to parse command-line arguments. There are a lot of options with argparse module.<\/p>\n\n\n\n