Command-line Input (parameters)

Question

I am very confused on how command-line input works, so for practice I was trying to take the following program down below and produce the same information but just by using command-line input, the only problem is I have no idea where to start

def main():
    x = (input("Give me a boolean: ").lower() == 'true')
    y = str(input("Give me a string: "))
    z = int(input("Give me a number: "))
    if x == True:
        print (y)
        print ("\"",y,"\"",sep="")
    else:
        print (z*2)



main()

@AaronHall, I agree that the questions aren't identical, but I'm hard-pressed to see how the **answers** to that question wouldn't also be applicable to this one. But yes, the one you found is even better. — Charles Duffy, Feb 26 '14 at 20:22

score 2 · Answer 1 · answered Feb 26 '14 at 20:07

2

See the description of sys.argv in http://docs.python.org/2/library/sys.html

import sys
x = sys.argv[1].lower() == 'true'
y = sys.argv[2]
z = int(sys.argv[3])

...or, to do things the Right Way, use argparse: http://docs.python.org/dev/library/argparse.html

answered Feb 26 '14 at 20:07

Charles Duffy

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My teacher has been teaching us with sys.argv, I've currently never seen the use of argparse. I am still very new to Python or any form of program for that matter haha – FootOfGork Feb 26 '14 at 20:19

score 1 · Answer 2 · edited May 23 '17 at 12:10

1

I agree with Charles to use argparse. I just wanted to add, that your main method should look like this:

def start(var):
    # ... your program start...

def parser():
    # use argparse here
    # ...
    return var

if __name__ == "__main__":
    var = parser()
    start(var)
    # ...

You can read the reason in the answers to this question

edited May 23 '17 at 12:10

Community

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answered Feb 26 '14 at 20:14

runDOSrun

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Not passing var to start()? Decoupling command-line parsing from runtime execution is a Good Thing to be sure, but how exactly do you propose to get the parsed arguments out? – Charles Duffy Feb 26 '14 at 20:21
Woops, my bad. Thanks for the hint :) – runDOSrun Feb 26 '14 at 20:25

score 0 · Answer 3 · answered Feb 26 '14 at 20:22

0

For discovering how things work without reading the docs, the interactive interpreter is best.

>>> input("something: ")
something: true
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "<string>", line 1, in <module>
NameError: name 'true' is not defined
>>> input("something: ")
something: True
True
>>> input("something: ")
something: 12
12
>>> input("something: ")
something: 12.4
12.4
>>> type(input("something: "))
something: 14.3
<type 'float'>
>>> type(input("something: "))
something: 14
<type 'int'>

You see, it evaluates what the user writes as a Python value.

answered Feb 26 '14 at 20:22

Javier

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What does this have to do with the question (about accepting parameters **on the command line**)? – Charles Duffy Feb 26 '14 at 20:23
He tries to use the input function. – Javier Feb 26 '14 at 20:24

Command-line Input (parameters)

3 Answers3