Convert hex string to int in Python
Question
How do I convert a hex string to an int in Python?
I may have it as "0xffff
" or just "ffff
".
Solution
Without the 0x prefix, you need to specify the base explicitly, otherwise there's no way to tell:
x = int("deadbeef", 16)
With the 0x prefix, Python can distinguish hex and decimal automatically.
>>> print int("0xdeadbeef", 0)
3735928559
>>> print int("10", 0)
10
(You must specify 0
as the base in order to invoke this prefix-guessing behavior; omitting the second parameter means to assume base-10.)
OTHER TIPS
int(hexString, 16)
does the trick, and works with and without the 0x prefix:
>>> int("a", 16)
10
>>> int("0xa",16)
10
For any given string s:
int(s, 16)
Convert hex string to int in Python
I may have it as
"0xffff"
or just"ffff"
.
To convert a string to an int, pass the string to int
along with the base you are converting from.
Both strings will suffice for conversion in this way:
>>> string_1 = "0xffff"
>>> string_2 = "ffff"
>>> int(string_1, 16)
65535
>>> int(string_2, 16)
65535
Letting int
infer
If you pass 0 as the base, int
will infer the base from the prefix in the string.
>>> int(string_1, 0)
65535
Without the hexadecimal prefix, 0x
, int
does not have enough information with which to guess:
>>> int(string_2, 0)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 0: 'ffff'
literals:
If you're typing into source code or an interpreter, Python will make the conversion for you:
>>> integer = 0xffff
>>> integer
65535
This won't work with ffff
because Python will think you're trying to write a legitimate Python name instead:
>>> integer = ffff
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'ffff' is not defined
Python numbers start with a numeric character, while Python names cannot start with a numeric character.
Adding to Dan's answer above: if you supply the int() function with a hex string, you will have to specify the base as 16 or it will not think you gave it a valid value. Specifying base 16 is unnecessary for hex numbers not contained in strings.
print int(0xdeadbeef) # valid
myHex = "0xdeadbeef"
print int(myHex) # invalid, raises ValueError
print int(myHex , 16) # valid
The worst way:
>>> def hex_to_int(x):
return eval("0x" + x)
>>> hex_to_int("c0ffee")
12648430
Please don't do this!
Or ast.literal_eval
(this is safe, unlike eval
):
ast.literal_eval("0xffff")
Demo:
>>> import ast
>>> ast.literal_eval("0xffff")
65535
>>>
In Python 2.7, int('deadbeef',10)
doesn't seem to work.
The following works for me:
>>a = int('deadbeef',16)
>>float(a)
3735928559.0
The formatter option '%x' % seems to work in assignment statements as well for me. (Assuming Python 3.0 and later)
Example
a = int('0x100', 16)
print(a) #256
print('%x' % a) #100
b = a
print(b) #256
c = '%x' % a
print(c) #100
If you are using the python interpreter, you can just type 0x(your hex value) and the interpreter will convert it automatically for you.
>>> 0xffff
65535
with '0x' prefix, you might also use eval function
For example
>>a='0xff'
>>eval(a)
255