FTP script won't transfer remote files to local computer

Question

I have a C library with several datatypes which I have wrapped with Python and ctypes - works very well! In C I have the following (schematic) code:

typedef struct type1_struct type1_t;
typedef struct type2_struct type2_t;  

void some_function( type1_t *t1 , type2_t *t2) {  
  if (t2 == NULL) {  
     // Do whatever  
  } else {  
     // 
  }
}  

The main point in this code is that some_function() can take NULL as value for the t2 argument. In Python the type1_t and type2_t types are wrapped with classes Type1 and Type2 using the from_param() method:

Class Type1:
   def from_param(self):
       return self.c_ptr


   def call_some_func(self , arg2 = None):
       # This fails when the python/ctypes tries to
       # lookup the from_param() method and arg2 is None. 
       cfunc_some_function( self , arg2 )     


lib_handle = ctypes.CDLL( lib )
cfunc_some_function = getattr( lib_handle , "some_function")
cfunc_some_function.argtypes = [Type1 , Type2]

So the cfunc_some_function function is initialized to take a Type1 and Type2 instance as arguments, the ctypes layer will then call the from_param() methods of the two input arguments; however I would like the 'call_some_func()' method of the Type1 class to accept None for the arg2 argument, but then ctypes tries to call the from_param() method of the None object - which obviously fails.

So - I guess my question is: Is it possible to get the ctypes function call code to just pass NULL when it gets a None input argument?

Joakim

Solution

Before the mget command add a line that says

prompt

Comments

[Richard]

now this goes thru all files on remote folder, but keeps saying "port command successful. no such file" ... all files are there though ... any ideas?

[Richard]

same results ... loops thru all the files in the folder, and keeps saying "no such file" but all the files are there ... i use the same credentials as i use for GUI ftp access, so permissions should not be the issue ... any ideas?

[Richard]

didn't solve the issue but helped me get starter, thanx

[Stewart Robinson]

did you fix why the files weren't coming down?

[user422005]

OK; that was interesting. I have ~ 15 cases of from_param() as a instance method, and that has worked nicely for me (except this instance is None problem). I did as you suggested and it worked nicely. Thanks!

[Duncan]

I think it will work in most cases: Type.method(obj) and obj.method() are interchangeable when obj is an instance of Type, but ctypes can also call Type.method(obj) when obj is a different type such a None and that's what you've run into.

[Duncan]

@eryksun thanks: corrected. That's why I always write 'untested' when I can't test a code sample.