Using a loop to create multiple variables

Question

Let's say I need to make 5 variables. Since this may need to be adjusted in the future, I'm using a loop.

i = 0
for j in range(5):
    i += 1
    w[i] = function(i)

#results in:
    w1 = function(1)
    w2 = function(2)
    #etc...

I know the code above is incorrect. Is it possible to use a loop to create different variables?

hard to store a numpy array in a list and not get too complicated quickly, that's why I need individual vars. — i.., Oct 06 '17 at 14:16
Does this answer your question? [How do I create a variable number of variables?](https://stackoverflow.com/questions/1373164/how-do-i-create-a-variable-number-of-variables) — wjandrea, Jul 02 '20 at 01:29

Chetan_Vasudevan · Answer 1 · 2020-12-28T19:17:07.143

To create multiple variables you can use something like below, you use a for loop and store a pair of key-value, where key is the different variable names

    d={} #empty dictionary
    for x in range(1,10): #for looping 
        d["string{0}".format(x)]="Variable1"

The output looks like

{'string1': 'Variable1', 'string2': 'Variable1','string3': 'Variable1', 'string4': 'Variable1', 'string5':'Variable1', 'string6': 'Variable1', 'string7': 'Variable1','string8': 'Variable1', 'string9': 'Variable1'}

score 3 · Answer 2 · edited Oct 06 '17 at 14:14

3

You can create actual variables, but don't. Use a list

W = []
for j in range(5):
    ...
    W.append(function(i))

edited Oct 06 '17 at 14:14

BioGeek

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answered Oct 06 '17 at 14:11

blue_note

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For my purposes, they need to be vars (numpy is messy). Can you show how to do that? – i.. Oct 06 '17 at 14:15
what function do you want to use them in?? you can add them like `globals()['w1']=value`, but there's really no point in that. – blue_note Oct 06 '17 at 14:18
This may be `W.append(function(j))` instead of `W.append(function(i))` – DavidC. Oct 06 '17 at 14:18
@DavidC.: It would make sense but, weirdly, no. The OP says `function(i)` – blue_note Oct 06 '17 at 14:19

Neo · Answer 3 · 2017-10-06T14:18:33.723

You'd better just use a list. It's more readable and safer.
However, you can create variables in the global namespace using globals() dictionary:

i = 0
for j in range(5):
    i += 1
    globals()["w" + str(i)] = function(i)

Use it like this:

print (w1)

However, that's probably not a good idea. You can accidentally override something in the namespace, which will cause hard to debug bugs. Really, try not to do that.

If you want to call them by name and not by index (as in a list), use your own dictionary:

my_variables = {}
i = 0
for j in range(5):
    i += 1
    my_variables["w" + str(i)] = function(i)

Then use like this:

print (my_variables["w1"])

Using a loop to create multiple variables

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