Type comparison table
| ctypes type | C type | Python type |
|---|---|---|
| c_bool | _Bool | bool (1) |
| c_char | char | 1-character bytes object |
| c_wchar | wchar_t | 1-character string |
| c_byte | char | int |
| c_ubyte | unsigned char | int |
| c_short | short | int |
| c_ushort | unsigned short | int |
| c_int | int | int |
| c_uint | unsigned int | int |
| c_long | long | int |
| c_ulong | unsigned long | int |
| c_longlong | __int64 or long long | int |
| c_ulonglong | unsigned __int64 or unsigned long long | int |
| c_size_t | size_t | int |
| c_ssize_t | ssize_t or Py_ssize_t | int |
| c_float | float | float |
| c_double | double | float |
| c_longdouble | long double | float |
| c_char_p | char * (NUL terminated) | bytes object or None |
| c_wchar_p | wchar_t * (NUL terminated) | string or None |
| c_void_p | void * | int or None |
- Between char and wchar, one is C-type single-byte encoding and the other is Unicode two-byte encoding, which can usually be converted to each other by decode and encode.
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Normal type assignment
Since python is untyped, once an object is created and assigned, assigning it again will become a new type. So assignments are usually made in the form of classes or containers.That is, assign values by adding attributes.
Normal type assignment
from ctypes import * a = c_int(2) print(type(a)) a = 2 print(type(a)) a = c_int(2) a.value = 3 print(a) """ <class 'ctypes.c_long'> <class 'int'> c_long(3) [Finished in 0.1s] """Mismatch type assignment
If assignment is made to a non-corresponding type, it is first converted to the corresponding type, analogy C.
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String Creation
- C-style string
ctypes.create_string_buffer(init_or_size, size=None) Create a string buffer that can be modified, like char buffer[size]={init_or_size} The init_or_size must be of type int (indicating the creation size) or bytes for initialization.
from ctypes import * buf = create_string_buffer(10) print(sizeof(buf),buf,type(buf),buf.raw,buf.value) buf = create_string_buffer(b"test",10) print(sizeof(buf),buf,type(buf),buf.raw,buf.value) buf = create_string_buffer(b"test") print(sizeof(buf),buf,type(buf),buf.raw,buf.value) """ 10 <ctypes.c_char_Array_10 object at 0x037A9460> <class 'ctypes.c_char_Array_10'> b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' b'' 10 <ctypes.c_char_Array_10 object at 0x03835100> <class 'ctypes.c_char_Array_10'> b'test\x00\x00\x00\x00\x00\x00' b'test' 5 <ctypes.c_char_Array_5 object at 0x037A9460> <class 'ctypes.c_char_Array_5'> b'test\x00' b'test' [Finished in 0.1s] """ - Unicdoe style
ctypes.create_unicode_buffer(init_or_size, size=None) Create a character array buffer of Unicode type corresponding to a Python type c_wchar "ass" common type string and a C type wchar.
from ctypes import * buf = create_unicode_buffer(10) print(sizeof(buf),buf,type(buf),buf.value) buf = create_unicode_buffer("test",10) print(sizeof(buf),buf,type(buf),buf.value) buf = create_unicode_buffer("test") print(sizeof(buf),buf,type(buf),buf.value) """ 20 <ctypes.c_wchar_Array_10 object at 0x00AB94F0> <class 'ctypes.c_wchar_Array_10'> 20 <ctypes.c_wchar_Array_10 object at 0x02B15100> <class 'ctypes.c_wchar_Array_10'> test 10 <ctypes.c_wchar_Array_5 object at 0x00AB94F0> <class 'ctypes.c_wchar_Array_5'> test [Finished in 0.1s] """
- C-style string
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Types that can be used generically.
There are several types that can be used directly like the C type, such as int, string,bytes, which can be compared with the above types.All matches can be used directly.
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Custom types as parameters.