# python int to hex string - Convert hex string to int in Python

`int(hexString, 16)` does the trick, and works with and without the 0x prefix:

``````>>> int("a", 16)
10
>>> int("0xa",16)
10
``````
python string to hex

How do I convert a hex string to an int in Python?

I may have it as "`0xffff`" or just "`ffff`".

# 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
``````

The worst way:

``````>>> def hex_to_int(x):
return eval("0x" + x)

>>> hex_to_int("c0ffee")
12648430
``````

Is using eval in Python a bad practice?

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
``````

with '0x' prefix, you might also use eval function

For example

``````>>a='0xff'
>>eval(a)
255
``````

### Tags

python   string   hex