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POResize ctypes array
 

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    <p>I'd like to resize a ctypes array. As you can see, ctypes.resize doesn't work like it could. I can write a function to resize an array, but I wanted to know some other solutions to this. Maybe I'm missing some ctypes trick or maybe I simply used resize wrong. The name c_long_Array_0 seems to tell me this may not work with resize.</p> <pre><code>&gt;&gt;&gt; from ctypes import * &gt;&gt;&gt; c_int * 0 &lt;class '__main__.c_long_Array_0'&gt; &gt;&gt;&gt; intType = c_int * 0 &gt;&gt;&gt; foo = intType() &gt;&gt;&gt; foo &lt;__main__.c_long_Array_0 object at 0xb7ed9e84&gt; &gt;&gt;&gt; foo[0] Traceback (most recent call last): File "&lt;stdin&gt;", line 1, in &lt;module&gt; IndexError: invalid index &gt;&gt;&gt; resize(foo, sizeof(c_int * 1)) &gt;&gt;&gt; foo[0] Traceback (most recent call last): File "&lt;stdin&gt;", line 1, in &lt;module&gt; IndexError: invalid index &gt;&gt;&gt; foo &lt;__main__.c_long_Array_0 object at 0xb7ed9e84&gt; &gt;&gt;&gt; sizeof(c_int * 0) 0 &gt;&gt;&gt; sizeof(c_int * 1) 4 </code></pre> <p>Edit: Maybe go with something like:</p> <pre><code>&gt;&gt;&gt; ctypes_resize = resize &gt;&gt;&gt; def resize(arr, type): ... tmp = type() ... for i in range(len(arr)): ... tmp[i] = arr[i] ... return tmp ... ... &gt;&gt;&gt; listType = c_int * 0 &gt;&gt;&gt; list = listType() &gt;&gt;&gt; list = resize(list, c_int * 1) &gt;&gt;&gt; list[0] 0 &gt;&gt;&gt; </code></pre> <p>But that's ugly passing the type instead of the size. It works for its purpose and that's it.</p>
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    1. COScott, I forgot one thing. I think if your array was initialized like we are doing it (without mallocing a block, letting ctypes do it) then you need to keep a reference to the original object in the new ctypes object, because I think the memory is freed when the first object dies. So you will need to do "if hasattr(array,"original"), newarray.original = array.original, else newarray.original = array". Then the garbage collector will trash the original array which in turn frees the block. If you need help just ask in the comments box.
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    2. COGotcha. I ran into a problem where I couldn't resize a _field_ member in a ctypes Structure. Something about the memory not being owned or something. Not a huge deal.
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    3. COOk, I think I'm running into a gc issue: python: Modules/gcmodule.c:241: update_refs: Assertion `gc->gc.gc_refs == (-3)' failed.
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