CODEWITHSUNDEEP
python-3.xctypes
jacob
jacob

Reputation: 4956

Python3 ctypes c_char array converted to immutable bytes type?

I've defined a structure:

class test(Structure):
    _fields_ = [('char_array', c_char * 255)]

a = test()

# prints <class 'bytes'>
print(type(a.char_array))

Why is this type bytes and not type bytearray? I'm unable to change values in char_array because bytes doesn't support item assignment. i.e: a.char_array[0] = 1

This isn't the case if instead I were to use c_int; just curious why ctypes is converting this to a bytes object and not leaving it as c_char_Array_255 like it would if it were c_int * 255?

How do I convert it to a bytearray and still modify the structure accordingly?

Upvotes: 2

Views: 1443

Answers (1)

Jean-Fran&#231;ois Fabre
Jean-Fran&#231;ois Fabre

Reputation: 140186

Type c_char maps to immutable type.

Use type c_byte to be able to modify that. Example:

from ctypes import *

class test(Structure):
    _fields_ = [('char_array', c_byte * 255)]

a = test()

print(type(a.char_array))
a.char_array[0]=ord('e')
a.char_array[1]=ord('x')
print(bytes(a.char_array).decode())

prints ex

Upvotes: 2

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