Getting the name of a variable as a string

Question

This thread discusses how to get the name of a function as a string in Python: How to get a function name as a string?

How can I do the same for a variable? As oppose

Answer 1

Here's one approach. I wouldn't recommend this for anything important, because it'll be quite brittle. But it can be done.

Create a function that uses the inspect module to find the source code that called it. Then you can parse the source code to identify the variable names that you want to retrieve. For example, here's a function called autodict that takes a list of variables and returns a dictionary mapping variable names to their values. E.g.:

x = 'foo'
y = 'bar'
d = autodict(x, y)
print d

Would give:

{'x': 'foo', 'y': 'bar'}

Inspecting the source code itself is better than searching through the locals() or globals() because the latter approach doesn't tell you which of the variables are the ones you want.

At any rate, here's the code:

def autodict(*args):
    get_rid_of = ['autodict(', ',', ')', '\n']
    calling_code = inspect.getouterframes(inspect.currentframe())[1][4][0]
    calling_code = calling_code[calling_code.index('autodict'):]
    for garbage in get_rid_of:
        calling_code = calling_code.replace(garbage, '')
    var_names, var_values = calling_code.split(), args
    dyn_dict = {var_name: var_value for var_name, var_value in
                zip(var_names, var_values)}
    return dyn_dict

The action happens in the line with inspect.getouterframes, which returns the string within the code that called autodict.

The obvious downside to this sort of magic is that it makes assumptions about how the source code is structured. And of course, it won't work at all if it's run inside the interpreter.

Answer 2

I think it's so difficult to do this in Python because of the simple fact that you never will not know the name of the variable you're using. So, in his example, you could do:

Instead of:

list_of_dicts = [n_jobs, users, queues, priorities]

dict_of_dicts = {"n_jobs" : n_jobs, "users" : users, "queues" : queues, "priorities" : priorities}

Answer 3

This function will print variable name with its value:

import inspect

def print_this(var):
    callers_local_vars = inspect.currentframe().f_back.f_locals.items()
    print(str([k for k, v in callers_local_vars if v is var][0])+': '+str(var))

***Input & Function call:***
my_var = 10

print_this(my_var)

***Output**:*
my_var: 10

Answer 4

just another way to do this based on the content of input variable:

(it returns the name of the first variable that matches to the input variable, otherwise None. One can modify it to get all variable names which are having the same content as input variable)

def retrieve_name(x, Vars=vars()):
    for k in Vars:
        if type(x) == type(Vars[k]):
            if x is Vars[k]:
                return k
    return None

Answer 5

If the goal is to help you keep track of your variables, you can write a simple function that labels the variable and returns its value and type. For example, suppose i_f=3.01 and you round it to an integer called i_n to use in a code, and then need a string i_s that will go into a report.

def whatis(string, x):
    print(string+' value=',repr(x),type(x))
    return string+' value='+repr(x)+repr(type(x))
i_f=3.01
i_n=int(i_f)
i_s=str(i_n)
i_l=[i_f, i_n, i_s]
i_u=(i_f, i_n, i_s)

## make report that identifies all types
report='\n'+20*'#'+'\nThis is the report:\n'
report+= whatis('i_f ',i_f)+'\n'
report+=whatis('i_n ',i_n)+'\n'
report+=whatis('i_s ',i_s)+'\n'
report+=whatis('i_l ',i_l)+'\n'
report+=whatis('i_u ',i_u)+'\n'
print(report)

This prints to the window at each call for debugging purposes and also yields a string for the written report. The only downside is that you have to type the variable twice each time you call the function.

I am a Python newbie and found this very useful way to log my efforts as I program and try to cope with all the objects in Python. One flaw is that whatis() fails if it calls a function described outside the procedure where it is used. For example, int(i_f) was a valid function call only because the int function is known to Python. You could call whatis() using int(i_f**2), but if for some strange reason you choose to define a function called int_squared it must be declared inside the procedure where whatis() is used.

Answer 6

Many of the answers return just one variable name. But that won't work well if more than one variable have the same value. Here's a variation of Amr Sharaki's answer which returns multiple results if more variables have the same value.

def getVariableNames(variable):
    results = []
    globalVariables=globals().copy()
    for globalVariable in globalVariables:
        if id(variable) == id(globalVariables[globalVariable]):
            results.append(globalVariable)
    return results

a = 1
b = 1
getVariableNames(a)
# ['a', 'b']