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Use variable to hold a variable name

HowTo

Use variable to hold a variable name

by  Bong  Posted    (Edited  )
This may be the long way around the barn but sometimes it comes up that you want the value of a variable, say that it is input from a file, to be the name of a variable in the code. It wasn't obvious to me how to do it and here is at least "a way":

For example, let a='x', that is the value of variable a is the string, 'x'. This could be the result of a file read, like a=f.readline().split()[0], or something. Anyway, the value of the variable, a, is the string that is to be used as a variable name, in this case, "x".

Now we need to use the compile built-in function to build an object that can be evaluated:
Code: 
c=compile(a+'=42','<string>','exec')
where "=42" could be any assignment.

Then we use eval() to substitute the value of a (or x) into the compiled object:
Code: 
eval(c)

Now, the variable whose name is x is equal to 42.
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