hex string to hex value

[tim]

This is probably another newbie question...but...
even after reading quite some messages like '..hex to decimal',
'creating a hex value' , I can't figure this out:
If i do'0x42'
i cannot use n as value for a variable that takes hex values, because it
throws:

error: required argument is not an integer
gives me:
Traceback (most recent call last):
File "<interactive input>", line 1, in ?
ValueError: invalid literal for int(): 0x42

how do I convert '0x42' to 0x42 ?

thanks!

 

[avnit]

If you just want to convert a string to an integer, it would be:

in your case it would be:

 

[mensanator]

If you just want to convert a string to an integer, it would be:

That's what the OP tried and it didn't work.

BECAUSE you have to tell the int function what base the string is in
(even though it has "0x" at the start).

66


in your case it would be:

Wrong again, you still have to tell it what base.
66

 

[tim]

but then i get :
Traceback (most recent call last):

what am I missing here ?
thank you
Tim

 

[mensanator]

but then i get :

Traceback (most recent call last):


what am I missing here ?

Avnit's solution was wrong. When converting a string, you
must state what base you are converting from.
66

Fredrik Lundh's solution works if the hex string starts with "0x"
(which it will when the string is created with the hex function).
66

But it won't work without the "0x".

Traceback (most recent call last):
File "<pyshell#18>", line 1, in -toplevel-
int('1A',0)
ValueError: invalid literal for int(): 1A

 

[tim]

tim wrote:



Avnit's solution was wrong. When converting a string, you
must state what base you are converting from.



66

Fredrik Lundh's solution works if the hex string starts with "0x"
(which it will when the string is created with the hex function).

aren't you converting from a hex string to a decimal value here?

 

[Grant Edwards]

aren't you converting from a hex string to a decimal value here?

No.

He's converting from a hex string to an integer object.

 

[Fredrik Lundh]

Fredrik Lundh's solution works if the hex string starts with "0x"

that's what "interpret [it] as a Python literal" meant.

(which it will when the string is created with the hex function).

66

But it won't work without the "0x".


Traceback (most recent call last):
File "<pyshell#18>", line 1, in -toplevel-
int('1A',0)
ValueError: invalid literal for int(): 1A

as the error message says, 1A isn't a valid literal.

</F>

 

[mensanator]

Fredrik Lundh's solution works if the hex string starts with "0x"

that's what "interpret [it] as a Python literal" meant.

I know from personal experience that the implications of that
sometimes go right over the head of a newbie. Did I do something
wrong by pointing out exactly what that means? Isn't it better to
have the OP understand the problem than simply solve it for him?

as the error message says, 1A isn't a valid literal.

Yes, not all strings of valid hex characters are valid literals.
But surely you're not suggesting that the user simply give
up when faced with that situation?