Python Error ValueError need more than 1 value to unpack

Question

In Python  when I run this code   from sys import argv  script  user name  argv prompt     gt    print  Hi  s  I m the  s script      user name  script    I get this error   Traceback  most recent call last     script  user name  argv   ValueError  need more than 1 value to unpack   What does that error mean

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I assume you found this code on Exercise 14  Prompting And Passing   Do the following   script     some arguments    user name     some arguments     and that works perfectly

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You should run your code in a following manner in order get your output    python file name py user name

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You have to pass the arguments in the terminal in order to store them in  argv   This variable holds the arguments you pass to your Python script when you run it  It later unpacks the arguments and store them in different variables you specify in the program e g   script  first  second   argv print  Your file is    script print  Your first entry is    first print  Your second entry is   second   Then in your command line you have to run your code like this    python ex14 py Hamburger Pizza   Your output will look like this    Your file is  ex14 py Your first entry is  Hamburger Your second entry is  Pizza

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youre getting   ValueError  need more than 1 value to unpack    because you only gave one value  the script  which is ex14 py in this case   the problem is  that you forgot to add a name after you ran the  py file   line 3 of your code is   script  user name   argv   the script is ex14 py  you forgot to add a name after  so if your name was michael so what you enter into the terminal should look something like    gt  python ex14 py michael   make this change and the code runs perfectly

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This error is because   argv       which is argument variable that is holding the variables that you pass with a call to the script   so now instead   Python abc py  do  python abc py yourname  pass the variable that you made to store argv

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Probably you didn t provide an argument on the command line  In that case  sys argv only contains one value  but it would have to have two in order to provide values for both user name and script

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You shouldn t be doing tuple dereferencing on values that can change like your line below    script  user name   argv   The line above will fail if you pass less than one argument or more than one argument  A better way of doing this is to do something like this    for arg in argv 1         print arg   Of cause you will do something other than print the args  Maybe put a series of  if  statement in the  for  loop that set variables depending on the arguments passed  An even better way is to use the getopt or optparse packages

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You can t run this particular piece of code in the interactive interpreter  You ll need to save it into a file first so that you can pass the argument to it like this    python hello py user338690

[python] Python Error: "ValueError: need more than 1 value to unpack"

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