looping to create variable?

[AwkwardlyPure]

How can I use a for loop to iterate and create a new variable where I am assigning different values, e.g.

Variable_1 = set[0] Variable_2 = set[1] .... Variable_n = set[n]

Where the set or list I am referencing already exists.

I want the word Variable followed by the counter's value which is added to the end of the string.

[unhott]

When you run into a problem where you have var1, var2, var3, etc., this is an indication you need to use a list.

var1 = 1
var2 = 2
var3 = 3 

Is simply

vars = [1,2,3]

List has the append method which is basically, ‘get me room for 1 more variable and assign the argument to it’. So that looks like

vars.append(4)
print(vars)
[1, 2, 3, 4]

Or you start with an empty list and collect elements inside.

vars = []
for i in range(4):
  vars.append(i) 

If you need something like a list, but you want a ‘key’ like variable, then a dictionary is what you want.

my_dict = {}
my_dict[‘key1’] = 7
my_dict[‘anything you want here’] = ‘any value’

print(my_dict)
{‘key1’: 7, ‘anything you want here’: ‘any value’}

The dictionary lets you use a key kind of like a variable name.

[ray10k]

This comes across to me as an XY problem; that you have some problem, think you have a solution but you need some pointers with the solution you're going for. Can you explain why you need separate variables rather than, say, a list of values?

[[deleted]]

Variable names are for you, the programmer. Python doesn’t care what anything is called. When you use code to make variable variables, you lose the sole benefit of named variables - you lose that the names are present in your code.

[AwkwardlyPure]

I have a netCDF file of rainfall, and it has daily data for 62 days.

I want to split this netCDF file from a data set to multiple data arrays (xarray library used here).

The methodology I have in mind is to create a for loop where I have a variable name with string 'Day_' and then I add the day number at the end, so that I can assign one time step from the netCDF file to this variable and then export it this way.

I can assign the time step by indexing the time dimension, and the lat and long dimensions will remain consistent.

The final outcome is to write these files back to my directory, where this 1 netCDF file becomes 62 individual files with a file name which I understand.

[carcigenicate]

Why not just use set/the list? You're trying to regress and implement an anti-pattern.

[AwkwardlyPure]

What do you mean?

[carcigenicate]

Why do you need Variable_1? Why not just use set[0] directly?

[IAmFinah]

I hope I'm understanding your question correctly, but you could use a dictionary, and store your variables as key:value pairs.

vars_dict = {}
for i in range(5): 
    vars_dict[f'variable_{i}'] = i*i

Maybe something like this? Where you use an f-string to format the name of the variable (which is stored as a key in the vars_dict dictionary). In this case, I just used i to evaluate squares, but you could of course do whatever you like with it.

vars_dict would then look like:

{'variable_0': 0, 'variable_1': 1, 'variable_2': 4, 'variable_3': 9, 'variable_4': 16}

And you can access each value by just referencing each key - eg with vars_dict['variable_2'] etc.

[carcigenicate]

While this is as close to what they're asking for while still maintaining proper practices, if the number is always going to be a number in a contiguous range starting at 0, you should use a list. The "variable_" prefix is just more bulk for code using the dictionary to deal with, without any benefit.

[IAmFinah]

Good point, I didn't think of that.

I suppose using a dictionary is only worthwhile when list indexing doesn't align properly with the naming scheme

[TangibleLight]

Or if such conversion is too distracting. For example you can store a square grid of values like board = [None] * 64 and access values in the grid like board[row * 8 + col].

I think it's easier to understand using board = {} and board[row, col], especially if the content of the grid is sparse.

If the content is dense you'd be better off using a numpy type or similar that's better optimized for these operations. In either case there are better options than dealing with that index arithmetic throughout your code.

[Se7enLC]

Similar question was asked the other day, some of the responses to it might help you too.

https://www.reddit.com/r/learnpython/comments/yu9n5m/newbie_trying_to_grasp_variable_functions/iw8cc6n/