Multiple inputs for a python function

Question

I am starting with Python, and trying to make a function. The one i am in trouble is:

#~ this function should make a directory only if it doesn't exist
def make_dir(directoryname):
    if not os.path.exists(directoryname):
       return os.makedirs(directoryname)
    else: 
        print "la carpeta %s ya existe" %(directoryname)

What i want to know is if it is possible to give multiple inputs like

def make_dir(a,b,c,d,r)  #where a,b,c,d,r are directory names.

and how can i do it.

I apologize if it is an obvious question.

Use the `*args` syntax. This tells Python that a function can take a variable amount of arguments. — Christian Dean, Jun 12 '17 at 22:32
oh, oh. I wanted to avoid loops until i understand them better. I did not understand about `*args` but i will look in the web — , Jun 12 '17 at 22:36
See [Arbitrary Argument Lists](https://docs.python.org/3/tutorial/controlflow.html#arbitrary-argument-lists). — PM 2Ring, Jun 12 '17 at 22:36
i just need to add `*` inside the function, am i right? @PM2Ring — , Jun 12 '17 at 22:39
To work with `*args` properly you _will_ need to understand loops, especially the `for` loop. — PM 2Ring, Jun 12 '17 at 23:03

Christian Dean · Accepted Answer · 2017-06-12T23:22:23.903

3

Python has specific syntax for this. It is commonly referred to as *args. When Python sees this in a function definition, it allows the function caller to pass in a variable amount of arguments to the function.

The variable used in the *args syntax - which is a tuple - can then be used to access the arguments. In your case you can simply loop over the arguments and process them accordingly.

def make_dir(*dirs):
    for directory in dirs:
        if not os.path.exists(directory):
            return os.makedirs(directory)
        else:
            print "la carpeta %s ya existe" %(directory)

It is important to note you may name the args in *args anything you want. I renamed it dirs(short for directories). And while it is common practice to simply name it *args, in my opinion it is much better to rename it to fit each specific case. That way, you can clearly convey what kind of arguments your function expects.

edited Jun 12 '17 at 23:22

answered Jun 12 '17 at 22:42

Christian Dean

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And what if i just add `*` to the function in the original post? Would it be bad? – Jun 12 '17 at 22:51
@santimirandarp Opps! I just realized my code wouldn't work. You'd need to use a manual for loop instead. See my edits. – Christian Dean Jun 12 '17 at 23:01
This looks much better (to my unklowledge). I will try it. – Jun 12 '17 at 23:03
I am not sure but, shouldn't it be "if not os.path"..etc? – Jun 12 '17 at 23:16
@santimirandarp You correct. Thanks for catching the typo. – Christian Dean Jun 12 '17 at 23:22

score 1 · Answer 2 · answered Jun 12 '17 at 22:35

1

Either pass your variables as a sequence such as a tuple or list. Or use the splat operator * to unpack a variable amount of arguments.

i.e.

def foo(*args):
    return args

Sample Output:

>>> foo(1, 2, 3)
(1, 2, 3)

answered Jun 12 '17 at 22:35

ospahiu

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score 0 · Answer 3 · answered Jun 12 '17 at 22:44

You can use a variable arguments variable with *directorynames and use a for loop in the function:

import os

def make_dir(*directorynames):
    for dir_ in directorynames:
        if not os.path.exists(dir_):
            return os.makedirs(dir_)
        else: 
            print("la carpeta %s ya existe" %(dir_))

Regards.

Multiple inputs for a python function

3 Answers3