Question: IDAPython how to call bin_search ?

[winndy]

from idaapi import *
from idautils import *
from idc import *

"""
    bin_search(ea_t startEA, ea_t endEA, uchar image, uchar mask, 
        size_t len, int step, int flags) -> ea_t
    """
func = get_func(0x000E2324)
pattern = '123456'
mask = '000000'
ea = bin_search(func.startEA,func.endEA,pattern,mask,len(pattern),BIN_SEARCH_FORWARD,BIN_SEARCH_NOCASE)
#equal_bytes
print '%08lx'%(ea)

I call this script file, but got an error.

Traceback (most recent call last):
File "<string>", line 1, in <module>
File "C:\Program Files\IDA\python\init.py", line 60, in runscript
execfile(script, globals())
File "F:/test.py", line 12, in <module>
ea = bin_search(func.startEA,func.endEA,pattern,mask,len(pattern),BIN_SEARCH_FORWARD,BIN_SEARCH_NOCASE)
File "c:\Program Files\IDA\python\idaapi.py", line 12140, in bin_search
return _idaapi.bin_search(*args)
TypeError: in method 'bin_search', argument 3 of type 'uchar const *'

Any ideas?