How to Get a Function Name as a String

How to get a function name as a string?

my_function.__name__

Using __name__ is the preferred method as it applies uniformly. Unlike func_name, it works on built-in functions as well:

>>> import time
>>> time.time.func_name
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'builtin_function_or_method' object has no attribute 'func_name'
>>> time.time.__name__ 
'time'

Also the double underscores indicate to the reader this is a special attribute. As a bonus, classes and modules have a __name__ attribute too, so you only have remember one special name.

How to get a function's name as string?

greeting.capitalize is a function object, and that object has a .__name__ attribute that you can access. But greeting.capitalize() calls the function object and returns the capitalized version of the greeting string, and that string object doesn't have a .__name__ attribute. (But even if it did have a .__name__, it'd be the name of the string, not the name of the function used to create the string). And you can't do str.capitalize() because when you call the "raw" str.capitalize function you need to pass it a string argument that it can capitalize.

So you need to do

print str.capitalize.__name__

or

print greeting.capitalize.__name__

Get called function name as string

You need a C compiler that follows the C99 standard or later. There is a pre-defined identifier called __func__ which does what you are asking for.

void func (void)
{
  printf("%s", __func__);
}

Edit:

As a curious reference, the C standard 6.4.2.2 dictates that the above is exactly the same as if you would have explicitly written:

void func (void)
{
  static const char f [] = "func"; // where func is the function's name
  printf("%s", f);
}

Edit 2:

So for getting the name through a function pointer, you could construct something like this:

const char* func (bool whoami, ...)
{
  const char* result;

  if(whoami)
  {
    result = __func__;
  }
  else
  {
    do_work();
    result = NULL;
  }

  return result;
}

int main()
{
  typedef const char*(*func_t)(bool x, ...); 
  func_t function [N] = ...; // array of func pointers

  for(int i=0; i<N; i++)
  {
    printf("%s", function[i](true, ...);
  }
}

How to execute a JavaScript function when I have its name as a string

Don't use eval unless you absolutely, positively have no other choice.

As has been mentioned, using something like this would be the best way to do it:

window["functionName"](arguments);

That, however, will not work with a namespace'd function:

window["My.Namespace.functionName"](arguments); // fail

This is how you would do that:

window["My"]["Namespace"]["functionName"](arguments); // succeeds

In order to make that easier and provide some flexibility, here is a convenience function:

function executeFunctionByName(functionName, context /*, args */) {
  var args = Array.prototype.slice.call(arguments, 2);
  var namespaces = functionName.split(".");
  var func = namespaces.pop();
  for(var i = 0; i < namespaces.length; i++) {
    context = context[namespaces[i]];
  }
  return context[func].apply(context, args);
}

You would call it like so:

executeFunctionByName("My.Namespace.functionName", window, arguments);

Note, you can pass in whatever context you want, so this would do the same as above:

executeFunctionByName("Namespace.functionName", My, arguments);

function name as a string

If you have a finite set of functions which you would like to be able to call I would recommend building a Map which maps Strings to instances of Runnable (or similar functional interfaces). Your useFunction method may then look up the function implementation in the Map and call it if it exists.

Example:

public class SomeClass {

    private final Map<String, Runnable> methods = new HashMap<>();
    {
        methods.put("helloworld", () -> {
            System.out.println("Hello World!");
        });
        methods.put("test", () -> {
            System.out.println("test!");
        });
        methods.put("doStuff", () -> {
            System.out.println("doStuff!");
        });
    }

    public void perform(String code) {
        methods.getOrDefault(code, 
            () -> {
                System.err.println("No such Method: "+code);
            })
        .run();
    }

}

If you want to call arbitrary methods you should probably use Reflection as stated by others.

Get function name as a string in python

That's simple.

print func.__name__

EDIT: But you must be careful:

>>> def func():
...     pass
... 
>>> new_func = func
>>> print func.__name__
func
>>> print new_func.__name__
func

Get function name to string

Sure, simply look into __name__:

>>> def foo(): pass
... 
>>> foo.__name__
'foo'

I have a string whose content is a function name, how to refer to the corresponding function in Python?

Since you are taking user input, the safest way is to define exactly what is valid input:

dispatcher={'add':add}
w='add'
try:
    function=dispatcher[w]
except KeyError:
    raise ValueError('invalid input')

If you want to evaluate strings like 'add(3,4)', you could use safe eval:

eval('add(3,4)',{'__builtins__':None},dispatcher)

eval in general could be dangerous when applied to user input. The above is safer since __builtins__ is disabled and locals is restricted to dispatcher. Someone cleverer than I might be able to still cause trouble, but I couldn't tell you how to do it.

WARNING: Even eval(..., {'__builtins__':None}, dispatcher) is unsafe to be applied to user input. A malicious user could run arbitrary functions on your machine if given the opportunity to have his string evaluated by eval.

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