python - parameters declaration ordering

Question

First of all, i'm very extremely noob, beginner etc. in python and programming in general, so sorry for the further questions but i have this sample code:

from sys import argv
p_script = argv 
p_user_name = argv
p_id = argv
v_prompt = ": "

print "Hey %s, I'm the %s script with id: '%s'" % (p_user_name, p_script, p_id)
print "I'd like to ask you a few questions."
print "Do you like me %s?" % p_user_name
v_likes = raw_input(v_prompt)

print "Where do you live %s?" % p_user_name
v_lives = raw_input(v_prompt)

print "What kind of computer do you have?"
v_computer = raw_input(v_prompt)

print """Alright, so you said '%s' about liking me.
You live in '%s'. Not sure where that is.
And you have a '%s' computer. Nice.""" % (v_likes, v_lives, v_computer)

and this:

from sys import argv
p_script, p_user_name, p_id = argv
v_prompt = ": "

print "Hey %s, I'm the %s script with id: '%s'" % (p_user_name, p_script, p_id)
print "I'd like to ask you a few questions."
print "Do you like me %s?" % p_user_name
v_likes = raw_input(v_prompt)

print "Where do you live %s?" % p_user_name
v_lives = raw_input(v_prompt)

print "What kind of computer do you have?"
v_computer = raw_input(v_prompt)

print """Alright, so you said '%s' about liking me.
You live in '%s'. Not sure where that is.
And you have a '%s' computer. Nice.""" % (v_likes, v_lives, v_computer)

i really don't understand why the output is crazy, like after passing the arguments or parameters as strings into the code when running it in powershell (i.e: exec python "example 1", "Name", "101") it gives me after each stept on run-time all the arguments. So what i'm trying to ask here, is why it doesn't works as-well correctly on different style o parameter declaration. See pls the declaration field of the first code snippet and the second declaration field i.e the "classic" style. Many Thanks, cheers.

argv is a list, you are currently assigning the whole list to all of the parameters. You need to use indexing to pass specific items in the list to the variables (e.g. argv[1]). Try read through this effbot.org/zone/python-list.htm — NDevox
– NDevox, Commented Mar 30, 2015 at 10:09

Daniel · Accepted Answer · 2015-03-30 10:10:02Z

3

You found the python list unpacking. In your first script

p_script = argv 
p_user_name = argv
p_id = argv

all three p_... have the same value argv. In the second script

p_script, p_user_name, p_id = argv

the list argv is unpacked, so that the first element becomes p_script, the second p_user_name and the third p_id.

answered Mar 30, 2015 at 10:10

Daniel

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Reut Sharabani · Accepted Answer · 2015-03-30 10:15:28Z

2

You are not using assignment correctly. You are assigning the list argv over and over instead of unpacking it, or assigning a single item from it instead of the entire list.

This part:

p_script, p_user_name, p_id = argv

Is not equivalent to what you wrote, which assigns the list argv over and over:

p_script = argv 
p_user_name = argv
p_id = argv

It is, however, equivalent to this:

p_script = argv[0]
p_user_name = argv[1]
p_id = argv[2]

edited Mar 30, 2015 at 10:15

answered Mar 30, 2015 at 10:09

Reut Sharabani

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Comments

llogiq · Accepted Answer · 2015-03-30 10:10:10Z

1

The problem is in the first lines:

p_script = argv 
p_user_name = argv
p_id = argv

You probably meant to get elements from argv, like argv[0].

answered Mar 30, 2015 at 10:10

llogiq

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