How can you load a python script into memory and execute it as if it was the command line?

Question

I need to load a third-party python script into memory and then execute it as as if it was on the command line, similar to how in PowerShell you can do iex(new-object net.webclient).downloadstring("http://<my ip>/myscript.ps1") then invoke it.

For example, I'd like to have my test.py on a web server then locally download and execute it in memory with command line switches, something like:

load("http://<ip>/test.py")
exec("test.py -arg1 value -arg2 value")

I appreciate this is quite naive but any help is appreciated, thanks!

By passing it to the python interpreter. python myscript.py? — roganjosh
– roganjosh, Commented Jan 11, 2019 at 22:27
Thanks, but I mean that I already have a running python process which will be downloading and executing the script, and I don't want the test.py script to touch the disk, I just want to run it in memory? — m0rv4i
– m0rv4i, Commented Jan 11, 2019 at 22:29
I mean in order to execute test.py from my python process I don't want to download it to disk and run exec("python test.py -arg1 value -arg2 value") , I need to achieve that without test.py being written out. If test.py does IO that's fine. — m0rv4i
– m0rv4i, Commented Jan 11, 2019 at 22:34
@roganjosh yeah, the simplest solution would be to save the file to disk and use subprocess to execute the file, this would handle the args etc. It's interesting to think about though... — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Jan 11, 2019 at 22:43
@m0rv4i Two questions: 1. What is the reason that files cannot "touch" the hard drive? 2. If you have already identified a set of tools why can't you opt for a functional interface where the the input is the function's name and its arguments? — a_guest
– a_guest, Commented Jan 11, 2019 at 23:11

juanpa.arrivillaga · Accepted Answer · 2019-01-11 23:29:05Z

5

Here's a hacky way taking advantage of the -c option for the Python interpreter:

>>> import subprocess
>>> pycode = """
... import sys
... if sys.argv[1] == 'foo':
...     print('bar')
... else:
...     print('unrecognized arg')
... """
>>> result = subprocess.run(['python', '-c', pycode, 'bar'], stdout=subprocess.PIPE)
>>> print(result.stdout.decode())
unrecognized arg

>>> result = subprocess.run(['python', '-c', pycode, 'foo'], stdout=subprocess.PIPE)
>>> print(result.stdout.decode())
bar

This may come up with issues such as some platforms limiting the size of what you pass as arguments. I tried to do this using stdin, which the Python interpreter will accept, but then it won't accept arguments!

answered Jan 11, 2019 at 23:29

juanpa.arrivillaga

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Comments

Itz Wam · Accepted Answer · 2019-01-11 23:23:20Z

4

I would recommend you to download the script by using requests, and then execute it with exec.

Something like this :

import requests
url="https://gist.githubusercontent.com/mosbth/b274bd08aab0ed0f9521/raw/52ed0bf390384f7253a37c88c1caf55886b83902/hello.py"
r=requests.get(url)
script=r.text
exec(script)

Sources :

Why is Python's eval() rejecting this multiline string, and how can I fix it?

https://www.programiz.com/python-programming/methods/built-in/exec

http://docs.python-requests.org/en/master/

If you want to specify arguments to the downloaded script you can do this :

import requests
import sys
sys.argv = ['arg1', 'arg2']
url="https://gist.githubusercontent.com/itzwam/90cda6e05d918034e75c651448e6469e/raw/0bb293fba68b692b0a3d2b61274f5a075a13f06d/blahblah.py"
script=requests.get(url).text
exec(script)

gist:

import sys

class Example(object):
    def run(self):
        for arg in sys.argv:
            print arg
if __name__ == '__main__':
    Example().run()

Sources :

https://stackoverflow.com/a/14905087/10902809

edited Jan 11, 2019 at 23:23

answered Jan 11, 2019 at 22:53

Itz Wam

413 bronze badges

7 Comments

m0rv4i Over a year ago

Thanks! This looks close, however if I understand correctly it's going to execute the script line by line, right? What I'm looking for is to execute it in a similar way to the command line so I can pass args and the __main__ method gets called etc...?

juanpa.arrivillaga Over a year ago

This will not work. This just executes the script in the current modules namespace as if it were text in that module. You want to be able to, say, pass arguments to the script, and have it act as if you did python myscript.py in the command line

Itz Wam Over a year ago

you can easily specify arguments, but for the main method, i'm not sure PS: I tried it and it seems to call __main__

Itz Wam Over a year ago

I edited my message and added an example on how to add arguments

juanpa.arrivillaga Over a year ago

But this requires clobbering your main script's namespace with this dynamically executed module's namespace, and hackily sharing sys.argv.

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