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pythonvariablesfilenames
malekcellier
malekcellier

Reputation: 187

Variable name to string in Python

I have written some code in Python and I would like to save some of the variables into files having the name of the variable.

The following code:

variableName1 = 3.14
variableName2 = 1.09
save_variable_to_file(variableName1) # function to be defined
save_variable_to_file(variableName1)

should create 2 files, one named variableName1.txt and the other one variableName2.txt and each should contain the value of the corresponding variable at the time the function was called.

This variable name is supposed to be unique in the code.

Thanks!

HM

Upvotes: 6

Views: 4805

Answers (7)

Synthaze
Synthaze

Reputation: 6090

If you want to get the name of your variable as string, use python-varname package (python3):

from varname import nameof

s = 'Hey!'

print (nameof(s))

Output:

s

Get the package here:

https://github.com/pwwang/python-varname

Upvotes: 0

cdarke
cdarke

Reputation: 44354

It is possible to find the name of a variable, a called function can get its caller's variables using:

import sys

def save_variable_to_file(var):

     names = sys._getframe(1).f_globals
     names.update(sys._getframe(1).f_locals)
     for key in names.keys():
         if names[key] == var: 
             break

     if key:
         open(key+".txt","w").write(str(var))
     else:
         print(key,"not found")

thing = 42
save_variable_to_file(thing)

But it is probably a really bad idea. Note that I have converted the value to a string, how would you want dictionaries and lists to be saved? How are you going to reconstruct the variable later? 

import glob

for fname in glob.iglob("*.txt"):
    vname = fname.rstrip(".txt")
    value = open(fname).read()
    exec(vname + "=" + value)

print(locals())

Using something like exec can be a security risk, it is probably better to use something like a pickle, JSON, or YAML.

Upvotes: 2

martineau
martineau

Reputation: 123443

Variables don't have names. When your script runs it creates one or more identifiers for some of the objects it interacts with commonly called variables, but these are temporary and cease to exist when the program ends. Even if you save them, you will then be faced with the reverse problem of how to turn them back into an identifier with saved name associated with the saved value.

Upvotes: 0

glglgl
glglgl

Reputation: 91017

for key, value in locals().items():
    with open(key + '.txt', 'w') as f:
        f.write(value)

should do your trick - as long as all locally defined variables are to be considered.

A far better solution, however, would be to put all you need into a dict and act as the others already proposed.

You could even do this:

def save_files(**files):
    for key, value in files.items():
        with open(key + '.txt', 'w') as f:
            f.write(value)

and then

save_files(**my_previously_defined_dict)
save_files(**locals()) # as example above
save_files(filename='content')

Upvotes: 0

Michael
Michael

Reputation: 7736

No, this won't work. When you write the variable name there, it gives the value of the variable, 3.14 and so on, to save_variable_to_file(). Try one of these variants:

d = dict(my_variable_name=3.14)
save_variable_to_file('my_variable_name', d['my_variable_name'])

or:

var_name = 'my_variable_name'
d = {var_name: 3.14}
save_variable_to_file(var_name, d[var_name])

Here is a good tutorial, that you should definitely go through, if you're serious about learning Python.

Upvotes: 1

Netwave
Netwave

Reputation: 42678

How about using a dict:

var_dict = {'variable1': 3.14, 'variable2':1.09}
for key, value in var_dict.items():
    with open('path\%s'%key, "w") as file:
        file.write(value)

Upvotes: 0

Constantinius
Constantinius

Reputation: 35039

Unfortunately it is not possible to find out the name of a variable. Either you extend your function to also allow a string as a parameter, or you have to use another solution:

save_variable_to_file("variableName1", variableName1)

Another solution would be to store your variables within a dict which allows the retrieval of the keys as well:

myVariables = {}
myVariables["variableName1"] = 3.14


for key, value in myVariables.items():
    save_variable_to_file(key, value)

Upvotes: 0

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