Python convert string to variable name

Question

Im aware that this may come up as a duplicate but so far I haven't found (or should that be understood) an answer to what Im looking for.

I have a list of strings and want to convert each one into a variable name which I then assign something to. I understand that I may need a dict for this but I am unfamiliar with them as I am relatively new to python and all the examples I have seen so far deal with values whilst I'm trying something different.

Im after something like:

list = ['spam', 'eggs', 'ham']

for i in range(len(list)):
    list[i] = rat.readColumn(ratDataset, list[i])

where the first list[i] is a variable name and not a string. The second list[i] is a string (and for context is the name of a column Im reading from a raster attribute table (rat))

Essentially I want each string within the list to be set as a variable name.

The idea behind this is that I can create a loop without having to write out the line for each variable I want, with matching rat column name (the string). Maybe there is a beer way of doing this than I am suggesting?

Just use a dictionary, you should keep data out of variable names — jonrsharpe
– jonrsharpe, Commented Oct 2, 2014 at 10:33

pepr · Accepted Answer · 2014-10-02 12:09:41Z

3

Try the following:

lst = ['spam', 'eggs', 'ham']
d = {}   # empty dictionary
for name in lst:
    d[name] = rat.readColumn(ratDataset, name)

Do not use list for your identifiers as it is a type identifier and you would mask its existence. The for loop can iterate directly for the elements inside -- no need to construct index and use it aganist the list. The d['spam'] will be one of your variables.

Although, it is also possible to create the real variable names like spam, eggs, ham, you would not probably do that as the effect would be useless.

answered Oct 2, 2014 at 12:09

pepr

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1 Comment

pepr Over a year ago

:) Arthur was 14 seconds faster.

Arthur Vaïsse · Accepted Answer · 2014-10-02 12:09:27Z

Here comes a simple dictionary use :

variables = ['spam', 'eggs', 'ham']
data = {}

datum = 0

for variable in variables:
    data[variable] = datum
    datum+=1

print(data)
print("value : ",data[variables[2]])

It gives as result :

{'eggs': 1, 'ham': 2, 'spam': 0}
value : 2

NB : don't use list as a variable name, list is a type identifier that you can use to transform an object into a list if possible (list("abc")==['a', 'b', 'c']) and you are overriding it with your value list right now.

Fatemeh Asgarinejad · Accepted Answer · 2019-06-21 21:02:45Z

one way is setting the variable name as a string and changing a part or all of it via format() method and then using the string as a varibale via vars()[STRING]

import numpy as np
X1= np.arange(1,10)                                                                                                                                
y1=[i**2 for i in X1]                                                                                                                                
X2= np.arange(-5,5)                                                                                                                                
y2=[i**2 for i in X2]                                                                                                                          
for i in range(1,3): 
    X = 'X{}'.format(i) 
    y = 'y{}'.format(i) 
    print('X_{}'.format(i) , vars()[X])
    print('y_{}'.format(i) , vars()[y])

Output:


X_1 [1 2 3 4 5 6 7 8 9]
y_1 [1, 4, 9, 16, 25, 36, 49, 64, 81]
X_2 [-5 -4 -3 -2 -1  0  1  2  3  4]
y_2 [25, 16, 9, 4, 1, 0, 1, 4, 9, 16]

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