How to get a function's name as string?

Question

In Python, how do I get a function's name as a string?

I want to get the name of the str.capitalize() function as a string. It appears that the function has a __name__ attribute. When I do

print str.__name__

I get this output, as expected:

str

But when I run str.capitalize().__name__ I get an error instead of getting the name "capitalize".

> Traceback (most recent call last):
> File "string_func.py", line 02, in <module>  
>    print str.capitalize().__name__
> TypeError: descriptor 'capitalize' of 'str' object needs an argument

Similarly,

greeting = 'hello, world'
print greeting.capitalize().__name__

gives this error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'str' object has no attribute '__name__'

What went wrong?

What's wrong with `str.capitalize.__name__` or `greeting.capitalize.__name__`? — PM 2Ring, May 28 '17 at 11:15
If you want the name of the variable, you'd have to discover it separately https://stackoverflow.com/questions/2553354/how-to-get-a-variable-name-as-a-string-in-python — Peter Gibson, May 28 '17 at 11:17
@PM2Ring I got this `TypeError: descriptor 'capitalize' of 'str' object needs an argument` using `str.capitalize.__name__` — Asif Raza, May 28 '17 at 11:27
Make sure you're not adding brackets after capitalize in that statement — Peter Gibson, May 28 '17 at 11:30
Do you understand why adding the parentheses causes a problem? — PM 2Ring, May 28 '17 at 11:35
@PM2Ring `capitalize().__name__` not have an attribute `__name__` it is the problem. — Asif Raza, May 28 '17 at 11:39
`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 to capitalize. — PM 2Ring, May 28 '17 at 11:44
@PM2Ring can I use your description comment in my question solution section? — Asif Raza, May 28 '17 at 11:48
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/145305/discussion-between-a-raza-and-pm-2ring). — Asif Raza, May 28 '17 at 11:55
What is the purpose of getting a function name as a string? What will you do with the name? — Code-Apprentice, May 28 '17 at 14:09

score 11 · Accepted Answer · answered May 28 '17 at 16:35

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__

score 4 · Answer 2 · answered Jun 11 '17 at 17:53

Let's start from the error

Traceback (most recent call last):
File "", line 1, in
AttributeError: 'str' object has no attribute 'name'

Specific

AttributeError: 'str' object has no attribute 'name'

You are trying

greeting = 'hello, world'
print greeting.capitalize().__name__

Which will capitalize hello world and return it as a string.

As the error states, string don't have attribute _name_

capitalize() will execute the function immediately and use the result whereas capitalize will represent the function.

If you want to see a workaround in JavaScript,

Check the below snippet

function abc(){
  return "hello world";
}

console.log(typeof abc); //function
console.log(typeof abc());

So, don't execute.

Simply use

greeting = 'hello, world'
print greeting.capitalize.__name__

score 1 · Answer 3 · answered Jun 15 '17 at 08:06

1

You don't need to call this function and simply use name

>>> str.capitalize.__name__

answered Jun 15 '17 at 08:06

Erdenezul

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How to get a function's name as string?

3 Answers3