Execute python script inside a python script

Question

I have a scenario where i want to dynamically generate a python script - inside my main python script - store it as a string and then when need be, execute this dynamically generated script from my main script.

Is this possible, if so how?

thanks

• iandisme: That script sounds very, very painful.
• Moe: ... yo dawg ... knowyourmeme.com/memes/xzibit-yo-dawg

Answer 1

For a script in a file use exec

For a script in a string use eval

!!! But !!!

before you use strings passed in from an external source, sanity check them! Otherwise you expose the ability to execute arbitrary code from within you program, so range check your variables!

You do not ever want to be asking the question:

"excuse me mam, did you really name your son Robert'); DROP TABLE students; -- "?

If you dont understand the reference - see this quick cartoon...

http://xkcd.com/327/

but when you EVAL - you are taking full responsibility for the instructions that you are eval'ing.

• strager: Yes; check the input before eval'ing. One suggestion: can you use less ALLCAPS and use e.g. bold formatting (or no formatting at all)? It's somewhat hard to read the 'spaghetti post' with allcaps thrown in.
• George Lambert: sorry for the "spaghetti post" I have gotten much better in later messages with formatting

Answer 2

Read up on the execfile() function.

http://docs.python.org/library/functions.html?highlight=exec#execfile

Answer 3

May want to look at the statement exec: http://docs.python.org/release/2.5.2/ref/exec.html

Answer 4

If you want to execute the script within the context of the main script, you might want to check eval [ http://docs.python.org/py3k/library/functions.html#eval ]

Answer 5

Not sure how wise this is but isn't the exec function what you use if you need to execute Python code?

Answer 6

There is precedence for what you are trying to do. The collections.namedtuple function builds a template string which is passed to exec in order to build a dynamically defined class.

Answer 7

As of Python version 3.11, execfile (which was the most convenient function) is not listed as built-in function anymore.

@George Lambert answer is the way to go. I'll add just some code for quick reference.

Run script within script

To run the script "run_me.py" within the script "main.py" do this:

• run_me.py be like

print("hello_world")

• main.py be like

with open("run_me.py", "r") as fl:
 exec(fl.read())

Run code contained in a string

To run the code contained in a string us eval:

• main.py be like

string_w_py_code = "print('hello world')"
eval(string_w_py_code)