Generate Python variables dynamically

[Pedroski55]

For getting data from MySQL and displaying it in my output.php, I dynamically create PHP variables

$i = 0;
$j = 0;
foreach($allQsdata as $Qsdata) {
++$i;
$Qnr = 'Q' . $i;
${'Q'.$i} = $questions[$j];
++$j;
// other stuff
}

The I have PHP variables like: $Q1 , $Q2 ... These arre then passed to a function as the offset names of the data arrays collected from MySQL

I was just wondering, is it possible to dynamically create variables in Python? Just out of interest.

[perfringo]

Suggested reading: Why you don't want to dynamically create variables

[deanhystad]

If you have an object you can set attributes for the object

import junk

for name, value in zip('abc', (1, 2, 3)):
    setattr(junk, name, value)

print(junk.a, junk.b, junk.c)

Output:
1 2 3

What I don't know is how to get the module for the file you are in. I suppose you could use locals() or globals().

globals()['a'] = "I am a global a"
locals()['b'] = "I am a global b"

def func():
    locals()['b'] = "I am local b"
    locals()['c'] = "I am local c"
    print(a)
    print(b)
    print(c)

print(a)
print(b)

func()

Output:
I am a global a
I am a global b
I am a global a
I am a global b
Traceback (most recent call last):
  File "...", line 14, in <module>
    func()
  File "...", line 9, in func
    print(c)
NameError: name 'c' is not defined

Looks like locals() doesn't create variables in the local scope of the function. Not surprising.

I cannot fathom why you would ever want to do this. A variable is a convenient name you can use to access an object. Dynamically created names are not going to be convenient.

[ibreeden]

I was just wondering, is it possible to dynamically create variables in Python? Just out of interest.

Don't go that way. And why should you?

${'Q'.$i} = $questions[$j];

Why not use a dictionary?

Q = {}
...
Q[i] = questions[j]

[Pedroski55]

Thanks for the replies, interesting.

All I can say is, in PHP, I have found this very useful, since I have a function which returns an array with contents from MySQL and I need to collect X different arrays, depending on the number of questions, which varies. Barring writing static individual code for each week (PHP and me are not good friends), dynamically created variables are very useful!

[deanhystad]

If you think you need to create variables it just means you don't understand collections. If you really think about it, there are no variables in Python. a = a + 1 is locals["a"] = locals["a"] + 1

a = 1
print(a)
a = a  + 1
print(a)
locals()["a"] = locals()["a"] + 1
print(a, locals()["a"])

Output:
1
2
3 3

So anything you can do by dynamically making variables you could do with a dictionary. And a dictionary is better because it will only contain the keys you add. It not only keeps my things organized and together, it keeps everything else out. You can iterate through a dictionary of your PHP arrays and be comfortable knowing that all the items are PHP arrays. You also know you didn't accidentally overwrite something in the local scope.

I don't think dynamically created variables are bad. They are much worse than that.