Using for loop iterator for if condition

Question

I am new to python. I am looking python version of the following shell code.

 for (( i=1; i <= 5; i++ ))
 do
       if avg_$i > 0 ; then
       print "Yes!!"
       fi
 done

I tried this :

    for i in range(1,5):
         if(avg_%d != 0) %(i) :
            print("Yes !! ")

It is obvious in other languages. I am sure python will also have an easy way to do it.

what is `arg_` ? if it is list with arguments used when script was run then you have `sys.argv` for this. Normally you will have to use own list `arg` and `arg[i]` — furas, Dec 31 '16 at 15:28
http://stackoverflow.com/questions/9383740/what-does-pythons-eval-do — Prasanth, Dec 31 '16 at 15:28
I think you should use [`dictionary`](https://docs.python.org/2/tutorial/datastructures.html) for `_arg` variable — ᴀʀᴍᴀɴ, Dec 31 '16 at 15:32
As linked by @Prasanth you could use `eval` but it's risky and usually not recommended. Then the line `if(avg_%d != 0) %(i) :` would be `if(eval('avg_%d' % i) > 0) :` — UnholySheep, Dec 31 '16 at 15:44

furas · Accepted Answer · 2016-12-31T15:48:13.363

1

In Python you would use list arg instead of variables arg_1, arg_2, etc.

arg = [1, 4, -5, 15, -1]

for val in arg:
    if val > 0:
       print("yes")

So don't try to do it in the same way as in shell script.

If you really need with i then you would do

arg = [1, 4, -5, 15, -1]

for i in range(len(arg)):
    if arg[i] > 0:
       print("yes")

but version without range(len()) is better

Other method with i but without range(len())

arg = [1, 4, -5, 15, -1]

for i, val in enumerate(arg, 1):
    if val > 0:
       print("yes - element number", i)

EDIT: you can also keep it as dictionary

data = {
   'arg_1': 1, 
   'arg_2': 4, 
   'arg_3': -5, 
   'arg_4': 15,
   'arg_5': -1
}

for i in range(1, 6):
    if data['arg_{}'.format(i)] > 0:
       print("yes")

edited Dec 31 '16 at 15:48

answered Dec 31 '16 at 15:33

furas

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That's sad. I had some specific reason to use multiple variables. It's obvious to append in list. I thought python will have some way to deal with that. anyway, thanks .. – Grayrigel Dec 31 '16 at 15:38
you can also use dictionary `data["arg_{}".format(i) ] > 0` but it makes no sense if you can use list. – furas Dec 31 '16 at 15:42
Yeah. I think I will use a list. Thanks !! – Grayrigel Dec 31 '16 at 15:44

Using for loop iterator for if condition

1 Answers1