Exit to command line in Python

Question

I have a script that I want to exit early under some condition:

if not "id" in dir():
     print "id not set, cannot continue"
     # exit here!
# otherwise continue with the rest of the script...
print "alright..."
[ more code ]

I run this script using execfile("foo.py") from the Python interactive prompt and I would like the script to exit going back to interactive interpreter. How do I do this? If I use sys.exit(), the Python interpreter exits completely.

Answer 1

Put your code block in a method and return from that method, like such:

def do_the_thing():
    if not "id" in dir():
         print "id not set, cannot continue"
         return
         # exit here!
    # otherwise continue with the rest of the script...
    print "alright..."
    # [ more code ]

# Call the method
do_the_thing()

Also, unless there is a good reason to use execfile(), this method should probably be put in a module, where it can be called from another Python script by importing it:

import mymodule
mymodule.do_the_thing()

Answer 2

In the interactive interpreter; catch SystemExit raised by sys.exit and ignore it:

try:
    execfile("mymodule.py")
except SystemExit:
    pass

Answer 3

I'm a little obsessed with ipython for interactive work but check out the tutorial on shell embedding for a more robust solution than this one (which is your most direct route).

Answer 4

Instead of using execfile, you should make the script importable (name=='main protection, seperated into functions, etc.), and then call the functions from the interpreter.