[HELP]Open a python file using a python file

[SandSpur]

Not just opening some file automatically, that's easy. I want to know how to make a "enter program" function and it opens the program
My current code is this:

g='Prime Number Finder'
i=import program1 
program1 = prime_numbers.py.environ.get('Prime_numbers')
if program1 and prime_numbers.path.isfile(filename):
    execfile(prime_numbers.py)

print 'Programs available:'
print '1.', g
a=int(raw_input("Enter the program number: "))
while True:
	ok = raw_input(prompt)
	if ok in ('1'):
		return i
while True:
	pass

But I get a syntax error saying

i=import program1
^
SyntaxError: invalid syntax

How do I fix it?


--Additional Info--
*the file I'm trying to open is named prime_numbers.py
**prime_numbers.py is in a folder that run.py(the code above) is not in

[RedFaceofAwesomeness]

What is python file used for exactly.

[SandSpur]

What is python file used for exactly.

Anything you program it to do.
Python is a programming language, and that's exactly what I tend to do with it

Edit: I got help from someone now, request lock