尝试剥离“ 0x”时出错

Question

I am trying to strip of "0x" form the hex value using below code and running into error,can anyone suggest how to fix it?

   with open(r'\\Network\files\build_ver.txt','r+') as f:
        value = int(f.read(), 16)
        f.seek(0)
        write_value = hex(value + 1)
        final_value = format(write_value, 'x')
        f.write(final_value)

Error:-

Traceback (most recent call last):
  File "build_ver.py", line 5, in <module>
    final_value = format(write_value, 'x')
ValueError: Unknown format code 'x' for object of type 'str'

Answer 1

The hex built-in returns a string value:

>>> hex(123)
'0x7b'
>>> type(hex(123))
<class 'str'>
>>>

but format is expecting a hexadecimal value as its first argument:

>>> format('0x7b', 'x')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Unknown format code 'x' for object of type 'str'
>>>
>>> format(0x7b, 'x')
'7b'
>>>

Thus, it cannot be used here. Instead, you can just strip off the 0x with slicing:

with open(r'\\Network\files\build_ver.txt','r+') as f:
    value = int(f.read(), 16)
    f.seek(0)
    write_value = hex(value + 1)[2:]
    f.write(write_value)

[2:] will get every character in the string except for the first two. See a demonstration below:

>>> hex(123)
'0x7b'
>>> hex(123)[2:]
'7b'
>>>