Calling a Python file with arguments form within another Python file

You need to encapsulate your code correctly. You should have something like this:

y.py

def y_func(*args):
    # everything y does
if __name__ == "__main__":
    import sys
    y_func(*sys.argv)

x.py

from y import y_func
def x_func(*args):
    #do stuff
    y_result = y_func(*yargs)
    #finish x stuff
if __name__ == "__main__":
    import sys
    x_func(*sys.argv)

Try this

# y.py
import os
z='argument'
os.system('Python x.py '+z)

Using subprocess is better than os.system

import subprocess
subprocess.check_output(["ls", "-ltr"])

In your case let's say you have a.py:

import sys
print sys.argv[1:]

and in the prompt:

>>> import subprocess
>>> subprocess.check_output(["python", 'a.py', 'aaa bbb ccc'])
"['aaa bbb ccc']\n"
>>>