How do I extract the name of a variable as a string in a list comprehension?

Question

I am trying to extract the name of a variable as a string. I have defined two variables CurrentField and PreviousField and want to extract these names as strings to use elsewhere in my code.

CurrentField = ['One', 'Two']
PreviousField = ['One0', 'Two0']

def Updatedict(varname):
    callers_local_vars = inspect.currentframe().f_back.f_locals.items()
    stringvar = [k for k, v in callers_local_vars if v is varname][0]
    return stringvar

listofvars = [CurrentField, PreviousField]

ParameterDict = [Updatedict(keyname) for keyname in listofvars]

ParameterDict

All I get is a list saying ['keyname','keyname'] and what I am looking for is ['CurrentField','PreviousField'] .

How do I get my desired output?

Thanks a lot in advance.

You may find https://stackoverflow.com/questions/18425225/getting-the-name-of-a-variable-as-a-string/18425523 useful here. The bottom line is you effectively cannot programmatically get the name of a variable for most types of variables. Typically, when you see someone trying to find a variable name, the solution is almost always that they should use a dictionary instead. — codingatty, Jan 31 '19 at 03:53

score 3 · Accepted Answer · edited Jan 31 '19 at 23:05

3

What is wrong is your loop, try this (works for Python 3.6 according to F string prefix in python giving a syntax error) :


In [23]: my_dict = {}
    ...: i = 0
    ...: for var in listofvars:
    ...:     my_dict.update({f"var_{i}":Updatedict(var)[0]})
    ...:     i += 1

In [24]: my_dict
Out[24]: {'var_0': 'CurrentField', 'var_1': 'PreviousField'}

As a side note, functions should be lower_case, the same goes for variable names, upper case is for python classes

edited Jan 31 '19 at 23:05

AnalysisNerd

111
2
16

answered Jan 31 '19 at 03:53

Jose Angel Sanchez

729
9
20

1

I keep getting invalid syntax as the error message when I use your code. I am using python 3.5.5 . Apologies I didn't mention that earlier. – AnalysisNerd Jan 31 '19 at 21:15
1

I get the syntax error in this part of the code between the Quotation mark and the colon for {f"var_{i}":Updatedict(var) – AnalysisNerd Jan 31 '19 at 21:18
1

Change it yo only "i" (without quotes) – Jose Angel Sanchez Jan 31 '19 at 22:11
Weren't f-strings introduced to python 3.6? – hqkhan Jan 31 '19 at 22:14

AnalysisNerd · Answer 2 · 2019-01-31T22:11:47.300

1

If you are using a prior version of Python since the above code works for Python 3.6 onwards use this code:

my_dict = {}
i = 0
for var in listofvars:
    my_dict.update({"var_%s" %i : Updatedict(var)})
    i += 1

my_dict

edited Jan 31 '19 at 22:11

answered Jan 31 '19 at 22:01

AnalysisNerd

111
2
16

How do I extract the name of a variable as a string in a list comprehension?

2 Answers2