Loading a datalog program in a file into pyDatalog - logic-programming

Question

I am trying to use the pyDatalog.load() method to load a small pyDatalog program. For example, I am loading the factorial sample from https://sites.google.com/site/pydatalog/
from pyDatalog import pyDatalog
pyDatalog.create_atoms('factorial, N, F') # gives datalog capability to these words
def run_program():
N = pyDatalog.Variable()
F = pyDatalog.Variable()
file_in = open("sample_datalog_program.dl", 'r')
mc = file_in.read()
print mc
#pyDatalog.program()
def _(): # the function name is ignored
pyDatalog.load(mc)
#pyDatalog.load("""
#+ (factorial[1]==1)
#(factorial[N] == F) <= (N > 1) & (F == N*factorial[N-1])
#""")
print(pyDatalog.ask('factorial[4]==F'))
file_in.close()
pass
if __name__ == "__main__":
run_program()
the file sample_datalog_program.dl contains the following:
"""
+ (factorial[1]==1)
(factorial[N] == F) <= (N > 1) & (F == N*factorial[N-1])
"""
What am I doing wrong? When I replace the line pyDatalog.load(mc) by the next 4 commented lines it works fine.
The error I get is:
/usr/local/Cellar/python/2.7.3/Frameworks/Python.framework/Versions/2.7/bin/python2.7 run_datalog_program.py
pyDatalog version 0.12.0
Traceback (most recent call last):
File "run_datalog_program.py", line 25, in <module>
run_program()
File "run_datalog_program.py", line 11, in run_program
#pyDatalog.program()
File "/usr/local/lib/python2.7/site-packages/pyDatalog/pyParser.py", line 191, in add_program
load(source_code, newglobals, defined, function=func_name)
File "/usr/local/lib/python2.7/site-packages/pyDatalog/pyParser.py", line 154, in load
six.exec_(code, newglobals)
File "/usr/local/lib/python2.7/site-packages/six.py", line 308, in exec_
exec("""exec code in globs, locs""")
File "<string>", line 1, in <module>
File "_", line 1, in <module>
File "/usr/local/lib/python2.7/site-packages/pyDatalog/pyDatalog.py", line 115, in load
return pyParser.load(code)
File "/usr/local/lib/python2.7/site-packages/pyDatalog/pyParser.py", line 133, in load
spaces = r.match(line).group()
TypeError: expected string or buffer
"""
+ (factorial[1]==1)
(factorial[N] == F) <= (N > 1) & (F == N*factorial[N-1])
"""
Process finished with exit code 1
Thank you!

Answer 1

You should not mix the pyDatalog.load() API and the in-line API. See Dynamic Datalog statements (at bottom of page)
Here is how you could write your program:
from pyDatalog import pyDatalog
def run_program():
file_in = open("sample_datalog_program.dl", 'r')
mc = file_in.read()
print mc
pyDatalog.load(mc)
file_in.close()
print(pyDatalog.ask('factorial[3]==N'))
if __name__ == "__main__":
run_program()
The code in sample_datalog_program.dl should be (without triple quotes):
+ (factorial[1]==1)
(factorial[N] == F) <= (N > 1) & (F == N*factorial[N-1])