How to Get the Original Variable Name of Variable Passed to a Function

How to get the original variable name of variable passed to a function

You can't. It's evaluated before being passed to the function. All you can do is pass it as a string.

Determine original name of variable after its passed to a function

You're right, this is very much impossible in any sane way, since only the value gets passed into the function.

original variable name passed to function?

It's not possible. Even pass-by-reference won't help you. You'll have to pass the name as a second argument.

But what you have asked is most assuredly not a good solution to your problem.

python obtain variable name of argument in a function

You cannot do it like that (as Ignacio Vazquez-Abrams already answered), but you can do it in a similar way:

>>> def foo(**kwargs):
    for arg_name in kwargs:
        return kwargs[arg_name], arg_name

>>> foo(fib=1)
(1, 'fib')

The only difference is that you must use keyword arguments, otherwise it will not work.

The alternative solution is also to access __name__ attribute of passed variable, which will result in obtaining the name of function, class or name (or anything else that will have this name defined). The only thing that you should be aware of, is that by default this is not the name of the variable, but the original name of the function/class/module (the one assigned when it was being defined). See the example here: http://ideone.com/MzHNND

How to find the name of a variable that was passed to a function?

Not really solution, but may be handy (anyway you have echo('foo') in question):

def echo(**kwargs):
    for name, value in kwargs.items():
        print name, value

foo = 7
echo(foo=foo)

UPDATE: Solution for echo(foo) with inspect

import inspect
import re

def echo(arg):
    frame = inspect.currentframe()
    try:
        context = inspect.getframeinfo(frame.f_back).code_context
        caller_lines = ''.join([line.strip() for line in context])
        m = re.search(r'echo\s*\((.+?)\)$', caller_lines)
        if m:
            caller_lines = m.group(1)
        print caller_lines, arg
    finally:
        del frame

foo = 7
bar = 3
baz = 11
echo(foo)
echo(foo + bar)
echo((foo + bar)*baz/(bar+foo))

Output:

foo 7
foo + bar 10
(foo + bar)*baz/(bar+foo) 11

It has the smallest call, but it's sensitive to newlines, e.g.:

echo((foo + bar)*
      baz/(bar+foo))

Will print:

baz/(bar+foo)) 11

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