sys argv 1 meaning in script

Question

I m currently teaching myself Python and was just wondering  In reference to my example below  in simplified terms what the sys argv 1  represents  Is it simply asking for an input      usr bin python3 1    import modules used here -- sys is a very standard one import sys    Gather our code in a main   function def main      print   Hello there   sys argv 1       Command line args are in sys argv 1   sys argv 2         sys argv 0  is the script name itself and can be ignored    Standard boilerplate to call the main   function to begin   the program  if   name         main       main

User · Answer

sys argv is a list containing the script path and command line arguments  i e  sys argv 0  is the path of the script you re running and all following members are arguments

User · Answer

To pass arguments to your python script  while running a script via command line          python create thumbnail py test1 jpg test2 jpg      here  script name - create thumbnail py  argument 1 - test1 jpg  argument 2 - test2 jpg  With in the create thumbnail py script i use  sys argv 1     which give me the list of arguments i passed in command line as    test1 jpg    test2 jpg

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sys argv is a list   This list is created by your command line  it s a list of your command line arguments   For example   in your command line you input something like this   python3 2 file py something   sys argv will become a list   file py    something    In this case sys argv 1     something

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I would like to note that previous answers made many assumptions about the user s knowledge  This answer attempts to answer the question at a more tutorial level   For every invocation of Python  sys argv is automatically a list of strings representing the arguments  as separated by spaces  on the command-line  The name comes from the C programming convention in which argv and argc represent the command line arguments   You ll want to learn more about lists and strings as you re familiarizing yourself with Python  but in the meantime  here are a few things to know   You can simply create a script that prints the arguments as they re represented  It also prints the number of arguments  using the len function on the list   from   future   import print function import sys print sys argv  len sys argv     The script requires Python 2 6 or later  If you call this script print args py  you can invoke it with different arguments to see what happens    gt  python print args py   print args py   1   gt  python print args py foo and bar   print args py    foo    and    bar   4   gt  python print args py  foo and bar    print args py    foo and bar   2   gt  python print args py  foo and bar  and baz   print args py    foo and bar    and    baz   4   As you can see  the command-line arguments include the script name but not the interpreter name  In this sense  Python treats the script as the executable  If you need to know the name of the executable  python in this case   you can use sys executable   You can see from the examples that it is possible to receive arguments that do contain spaces if the user invoked the script with arguments encapsulated in quotes  so what you get is the list of arguments as supplied by the user   Now in your Python code  you can use this list of strings as input to your program  Since lists are indexed by zero-based integers  you can get the individual items using the list 0  syntax  For example  to get the script name   script name   sys argv 0    this will always work    Although interesting  you rarely need to know your script name  To get the first argument after the script for a filename  you could do the following   filename   sys argv 1    This is a very common usage  but note that it will fail with an IndexError if no argument was supplied   Also  Python lets you reference a slice of a list  so to get another list of just the user-supplied arguments  but without the script name   you can do  user args   sys argv 1     get everything after the script name   Additionally  Python allows you to assign a sequence of items  including lists  to variable names  So if you expect the user to always supply two arguments  you can assign those arguments  as strings  to two variables   user args   sys argv 1   fun  games   user args   len user args  had better be 2   So  to answer your specific question  sys argv 1  represents the first command-line argument  as a string  supplied to the script in question  It will not prompt for input  but it will fail with an IndexError if no arguments are supplied on the command-line following the script name

User · Answer

sys argv is a attribute of the sys module  It says the arguments passed into the file in the command line  sys argv 0  catches the directory where the file is located  sys argv 1  returns the first argument passed in the command line  Think like we have a example py file  example py import sys   Importing the main sys module to catch the arguments print sys argv 1     Printing the first argument  Now here in the command prompt when we do this  python example py  It will throw a index error at line 2  Cause there is no argument passed yet  You can see the length of the arguments passed by user using if len sys argv   gt   1    Code  If we run the example py with passing a argument python example py args  It prints  args  Because it was the first arguement  Let s say we have made it a executable file using PyInstaller  We would do this  example argumentpassed  It prints  argumentpassed  It s really helpful when you are making a command in the terminal  First check the length of the arguments  If no arguments passed  do the help text

User · Answer

Adding a few more points to Jason s Answer     For taking all user provided arguments    user args   sys argv 1    Consider the sys argv as a list of strings as  mentioned by Jason   So all the list manipulations will apply here  This is called  List Slicing   For more info visit here   The syntax is like this   list start end step   If you omit start  it will default to 0  and if you omit end  it will default to length of list   Suppose you only want to take all the arguments after 3rd argument  then     user args   sys argv 3     Suppose you only want the first two arguments  then     user args   sys argv 0 2   or  user args   sys argv  2    Suppose you want arguments 2 to 4    user args   sys argv 2 4    Suppose you want the last argument  last argument is always -1  so what is happening here is we start the count from back  So start is last  no end  no step     user args   sys argv -1    Suppose you want the second last argument    user args   sys argv -2    Suppose you want the last two arguments    user args   sys argv -2     Suppose you want the last two arguments  Here  start is -2  that is second last item and then to the end  denoted by         user args   sys argv -2     Suppose you want the everything except last two arguments  Here  start is 0  by default    and end is second last item    user args   sys argv  -2    Suppose you want the arguments in reverse order    user args   sys argv   -1    Hope this helps

User · Answer

sys  argv will display the command line args passed when running a script or you can say sys argv will store the command line arguments passed in python while running from terminal    Just try this    import sys print sys argv   argv stores all the arguments passed in a python list  The above will print all arguments passed will running the script   Now try this running your filename py like this   python filename py example example1   this will print 3 arguments in a list   sys argv 0   is the first argument passed  which is basically the filename     Similarly  argv1 is the first argument passed  in this case  example   A similar question has been asked already here btw  Hope this helps

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Just adding to Frederic s answer  for example if you call your script as follows      myscript py foo bar   sys argv 0  would be    myscript py   sys argv 1  would be  foo  and sys argv 2  would be  bar      and so forth   In your example code  if you call the script as follows    myscript py foo    the script s output will be  Hello there foo

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sys argv 1  contains the first command line argument passed to your script   For example  if your script is named hello py and you issue     python3 1 hello py foo  or     chmod  x hello py    make script executable     hello py foo   Your script will print   Hello there foo

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