Python: using a loop to do the same with several variables

Question

I have 30 variables with the pattern aod7039, aod7040, ...., aod7068. I want to do the same operation (i.e. calculate the mean over an axis) for all these variables and overwrite the original variables. Up to now I wrote 30 times the same line, and wondered if there isn't maybe an shorter and easier way to do this? I am gradeful for every idea!

You could combine all variable in a dictionary, which is iterable. — Tom de Geus
– Tom de Geus, Commented Mar 19, 2018 at 9:03
you could also use eval but keep that in mind eval is evil — Rajmani Arya
– Rajmani Arya, Commented Mar 19, 2018 at 9:06
Take a step back. Why do you have 30 similar variables? Is this not a misrepresentation of an array? — Yann Vernier
– Yann Vernier, Commented Mar 19, 2018 at 9:09
The number at the end of 'aod' is the year, and I want to do a time series over the 30 years. And unfortunately, there are 30 files, so I need to read in each variable separately from each file and then modify them a bit. — Leo
– Leo, Commented Mar 19, 2018 at 9:15
No you don't; you need to read in each file and then append to the same list or dict. No need for 39 variables. — Daniel Roseman
– Daniel Roseman, Commented Mar 19, 2018 at 9:16

ANDREYDEN · Accepted Answer · 2018-03-19 09:03:56Z

2

Firstly, don't use 30 variables, use a list aod[] Secondly, use

for i in range(7039, 7069):
    aod[i] = yourFunction(aod[i])

to override existing list

answered Mar 19, 2018 at 9:03

ANDREYDEN

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vishes_shell · Accepted Answer · 2018-03-19 09:03:10Z

2

This will get you all values of variables that start with 'aod'

values = [v for k,v in globals() if k.startswith('aod')]

But having 30 variables smells bad.

answered Mar 19, 2018 at 9:03

vishes_shell

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Dragin · Accepted Answer · 2018-03-19 09:08:18Z

1

If I understand your question right, you just want to iterate over those variables?

If so you could keep references on some list/dictionary and then iterate/update this way.

List = []
List.append(aod7039)
for item in List:
    #do something

answered Mar 19, 2018 at 9:08

Dragin

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bruno desthuilliers · Accepted Answer · 2018-03-19 09:16:48Z

1

I have 30 variables with the pattern aod7039, aod7040, ...., aod7068

Then you have a design problem - you should have a list or dict instead. Replace all those variables with either a list or dict (or collections.OrderedDict if you need key access while preserving insertion order) and then it's only a matter of iterating over your container, ie

# with a list:
for index, item in enumerate(yourlist):
    yourlist[index] = do_something_with(item)

# with a dict or OrderedDict:
for key, item in enumerate(yourdict):
    yourdic[key] = do_something_with(item)

answered Mar 19, 2018 at 9:16

bruno desthuilliers

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Kurumi Tokisaki · Accepted Answer · 2018-03-19 09:19:33Z

0

store your 30 variables in a list and use map to tackle it without any loop:

varlist=[aod7039, aod7040, ...., aod7068]
result=list(map(yourfunction, varlist))

answered Mar 19, 2018 at 9:19

Kurumi Tokisaki

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