On 02-Oct-16 19:50, Michael Felt wrote:
I am trying to understand the documentation re: ctypes and interfacing
with existing libraries.
I am reading the documentation, and also other sites that have largely
just copied the documentation - as well as the "free chapter" at
O'Reilly (Python Cookbook).
Using O'Reilly and the standard documentation I now have these two
excerpts. The second def works, the first does not.
Someone helping me understand what I am not reading properly in this bit
of documentation - is much appreciated.
from ctypes import c_int, WINFUNCTYPE, windll
from ctypes.wintypes import HWND, LPCSTR, UINT
prototype = WINFUNCTYPE(c_int, HWND, LPCSTR, LPCSTR, UINT)
paramflags = (1, "hwnd", 0), (1, "text", "Hi"), (1, "caption", None), (1,
"flags", 0)
MessageBox = prototype(("MessageBoxA", windll.user32), paramflags)
The MessageBox foreign function can now be called in these ways:
MessageBox()
MessageBox(text="Spam, spam, spam")
MessageBox(flags=2, text="foo bar")
Note that MessageBox() may give two arguments.
My code: note both def init() are meant to do the same thing, just different
call syntax.
+76 class cpu_total:
+77 def __init__(self):
+78 __perfstat__ = CDLL("libperfstat.a(shr_64.o)")
+79 prototype = CFUNCTYPE(c_int, c_void_p, c_void_p, c_int, c_int)
+80 args = (1, "name", None), (2, "buff", None), (1, "size", 0), (1,
"count", 1)
+81 cpu_total = prototype(("perfstat_cpu_total", __perfstat__),
args)
+82
+83 buff = perfstat_cpu_total_t()
+84 cpu_total(buff=buff, size=sizeof(buff))
+85
+86 class perfstat_cpu_total:
+87 def __init__(self):
+88 __perfstat__ = CDLL("libperfstat.a(shr_64.o)")
+89 cpu_total = __perfstat__.perfstat_cpu_total
+90
+91 _perfstat_cpu_total = perfstat_cpu_total_t()
+92 ret = cpu_total(None,
+93 byref(_perfstat_cpu_total),
+94 sizeof(perfstat_cpu_total_t), 1)
+95 self.boot = _perfstat_cpu_total.lbolt.v / 100
+96 self.ncpus = _perfstat_cpu_total.ncpus
+97 self._v = _perfstat_cpu_total
When I call the second I can print values and even call functions, reload the
_v, etc..
The first class fails with this message:
a = cpu_total()
Traceback (most recent call last):
File "<stdin>", line 135, in <module>
File "<stdin>", line 84, in __init__
TypeError: call takes exactly 1 arguments (2 given)
Thanks for your attention.
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