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Python: ctypes how to convert c_char_Array into c_char_p
2019 Community Moderator ElectionHow to merge two dictionaries in a single expression?How do I check whether a file exists without exceptions?Calling an external command in PythonWhat are metaclasses in Python?Finding the index of an item given a list containing it in PythonHow can I safely create a nested directory in Python?Does Python have a ternary conditional operator?How to get the current time in PythonHow can I make a time delay in Python?Does Python have a string 'contains' substring method?
The function create_string_buffer(b"foo", 3) returns a type c_char_Array_3. Trying to pass this in where c_char_p is expected blows up with TypeError: incompatible types, c_char_Array_3 instance instead of c_char_p instance. How do I pass the output of create_string_buffer into a field that expects c_char_p?
I think this person had the same question: https://ctypes-users.narkive.com/620LJv10/why-doesn-t-c-char-array-get-coerced-on-assignment-to-a-pointer
However, it's unclear to me what the answer was.
python ctypes
asked Mar 7 at 18:42
TommyTommy
5,08653460
add a comment |
The function create_string_buffer(b"foo", 3) returns a type c_char_Array_3. Trying to pass this in where c_char_p is expected blows up with TypeError: incompatible types, c_char_Array_3 instance instead of c_char_p instance. How do I pass the output of create_string_buffer into a field that expects c_char_p?
I think this person had the same question: https://ctypes-users.narkive.com/620LJv10/why-doesn-t-c-char-array-get-coerced-on-assignment-to-a-pointer
However, it's unclear to me what the answer was.
python ctypes
asked Mar 7 at 18:42
TommyTommy
5,08653460
add a comment |
The function create_string_buffer(b"foo", 3) returns a type c_char_Array_3. Trying to pass this in where c_char_p is expected blows up with TypeError: incompatible types, c_char_Array_3 instance instead of c_char_p instance. How do I pass the output of create_string_buffer into a field that expects c_char_p?
I think this person had the same question: https://ctypes-users.narkive.com/620LJv10/why-doesn-t-c-char-array-get-coerced-on-assignment-to-a-pointer
However, it's unclear to me what the answer was.
python ctypes
asked Mar 7 at 18:42
TommyTommy
5,08653460
The function create_string_buffer(b"foo", 3) returns a type c_char_Array_3. Trying to pass this in where c_char_p is expected blows up with TypeError: incompatible types, c_char_Array_3 instance instead of c_char_p instance. How do I pass the output of create_string_buffer into a field that expects c_char_p?
I think this person had the same question: https://ctypes-users.narkive.com/620LJv10/why-doesn-t-c-char-array-get-coerced-on-assignment-to-a-pointer
However, it's unclear to me what the answer was.
python ctypes
python ctypes
asked Mar 7 at 18:42
TommyTommy
5,08653460
asked Mar 7 at 18:42
TommyTommy
5,08653460
edited Mar 7 at 18:48
Tommy
asked Mar 7 at 18:42
TommyTommy
5,08653460
asked Mar 7 at 18:42
TommyTommy
5,08653460
asked Mar 7 at 18:42
TommyTommy
5,08653460
5,08653460
add a comment |
add a comment |
1 Answer
1
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oldest
votes
You can pass a create_string_buffer object to a function with a c_char_p as an .argtypes parameter, but not when it is a member of a structure. cast can work around it. This was mentioned in the link you provided in the question.
from ctypes import *
class foo(Structure):
_fields_ = [('bar',c_char_p)]
s = create_string_buffer(b'test')
f = foo()
f.bar = cast(s,c_char_p)
print(f.bar)
s[0] = b'q'
print(f.bar)
Output:
b'test'
b'qest'
answered Mar 7 at 23:25
Mark TolonenMark Tolonen
95.4k12115177
add a comment |
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1 Answer
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1 Answer
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active
oldest
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oldest
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active
oldest
votes
You can pass a create_string_buffer object to a function with a c_char_p as an .argtypes parameter, but not when it is a member of a structure. cast can work around it. This was mentioned in the link you provided in the question.
from ctypes import *
class foo(Structure):
_fields_ = [('bar',c_char_p)]
s = create_string_buffer(b'test')
f = foo()
f.bar = cast(s,c_char_p)
print(f.bar)
s[0] = b'q'
print(f.bar)
Output:
b'test'
b'qest'
answered Mar 7 at 23:25
Mark TolonenMark Tolonen
95.4k12115177
add a comment |
You can pass a create_string_buffer object to a function with a c_char_p as an .argtypes parameter, but not when it is a member of a structure. cast can work around it. This was mentioned in the link you provided in the question.
from ctypes import *
class foo(Structure):
_fields_ = [('bar',c_char_p)]
s = create_string_buffer(b'test')
f = foo()
f.bar = cast(s,c_char_p)
print(f.bar)
s[0] = b'q'
print(f.bar)
Output:
b'test'
b'qest'
answered Mar 7 at 23:25
Mark TolonenMark Tolonen
95.4k12115177
add a comment |
You can pass a create_string_buffer object to a function with a c_char_p as an .argtypes parameter, but not when it is a member of a structure. cast can work around it. This was mentioned in the link you provided in the question.
from ctypes import *
class foo(Structure):
_fields_ = [('bar',c_char_p)]
s = create_string_buffer(b'test')
f = foo()
f.bar = cast(s,c_char_p)
print(f.bar)
s[0] = b'q'
print(f.bar)
Output:
b'test'
b'qest'
answered Mar 7 at 23:25
Mark TolonenMark Tolonen
95.4k12115177
You can pass a create_string_buffer object to a function with a c_char_p as an .argtypes parameter, but not when it is a member of a structure. cast can work around it. This was mentioned in the link you provided in the question.
from ctypes import *
class foo(Structure):
_fields_ = [('bar',c_char_p)]
s = create_string_buffer(b'test')
f = foo()
f.bar = cast(s,c_char_p)
print(f.bar)
s[0] = b'q'
print(f.bar)
Output:
b'test'
b'qest'
answered Mar 7 at 23:25
Mark TolonenMark Tolonen
95.4k12115177
answered Mar 7 at 23:25
Mark TolonenMark Tolonen
95.4k12115177
answered Mar 7 at 23:25
Mark TolonenMark Tolonen
95.4k12115177
answered Mar 7 at 23:25
Mark TolonenMark Tolonen
95.4k12115177
95.4k12115177
add a comment |
add a comment |
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