## 问题：在Python中将十六进制字符串转换为int

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

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

## 回答 0

``x = int("deadbeef", 16)``

``````>>> print int("0xdeadbeef", 0)
3735928559
>>> print int("10", 0)
10
``````

（您必须指定`0`作为基准才能调用此前缀猜测行为；省略第二个参数意味着假定基准为10。）

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.)

## 回答 1

`int(hexString, 16)` 可以解决问题，并且可以使用和不使用0x前缀：

``````>>> int("a", 16)
10
>>> int("0xa",16)
10``````

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

``````>>> int("a", 16)
10
>>> int("0xa",16)
10
``````

## 回答 2

``int(s, 16)``

For any given string s:

``````int(s, 16)
``````

# 在Python中将十六进制字符串转换为int

``````>>> string_1 = "0xffff"
>>> string_2 = "ffff"
>>> int(string_1, 16)
65535
>>> int(string_2, 16)
65535``````

## 让`int`推断

``````>>> int(string_1, 0)
65535``````

``````>>> int(string_2, 0)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 0: 'ffff'``````

## 文字：

``````>>> integer = 0xffff
>>> integer
65535``````

``````>>> integer = ffff
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'ffff' is not defined``````

Python数字以数字字符开头，而Python名称不能以数字字符开头。

# 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
``````

## 回答 4

``````print int(0xdeadbeef) # valid

print int(myHex) # invalid, raises ValueError
print int(myHex , 16) # valid``````

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

print int(myHex) # invalid, raises ValueError
print int(myHex , 16) # valid
``````

## 回答 5

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

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

# 请不要这样做！

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?

## 回答 6

``ast.literal_eval("0xffff")``

``````>>> import ast
>>> ast.literal_eval("0xffff")
65535
>>> ``````

Or `ast.literal_eval` (this is safe, unlike `eval`):

``````ast.literal_eval("0xffff")
``````

Demo:

``````>>> import ast
>>> ast.literal_eval("0xffff")
65535
>>>
``````

## 回答 7

``````a = int('0x100', 16)
print(a)   #256
print('%x' % a) #100
b = a
print(b) #256
c = '%x' % a
print(c) #100``````

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
``````

## 回答 8

``````>>> 0xffff

65535``````

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
``````

## 回答 9

``````def to_number(n):
''' Convert any number representation to a number
This covers: float, decimal, hex, and octal numbers.
'''

try:
return int(str(n), 0)
except:
try:
# python 3 doesn't accept "010" as a valid octal.  You must use the
# '0o' prefix
return int('0o' + n, 0)
except:
return float(n)``````

Handles hex, octal, binary, int, and float

Using the standard prefixes (i.e. 0x, 0b, 0, and 0o) this function will convert any suitable string to a number. I answered this here: https://stackoverflow.com/a/58997070/2464381 but here is the needed function.

``````def to_number(n):
''' Convert any number representation to a number
This covers: float, decimal, hex, and octal numbers.
'''

try:
return int(str(n), 0)
except:
try:
# python 3 doesn't accept "010" as a valid octal.  You must use the
# '0o' prefix
return int('0o' + n, 0)
except:
return float(n)
``````

## 回答 10

``````>>a = int('deadbeef',16)
>>float(a)
3735928559.0``````

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
``````

## 回答 11

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

with ‘0x’ prefix, you might also use eval function

For example

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