Execute shell commands in Python

The first command simply writes to a file. You wouldn't execute that as a shell command because python can read and write to files without the help of a shell:

with open('/proc/sys/net/ipv4/ip_forward', 'w') as f:
    f.write("1")

The iptables command is something you may want to execute externally. The best way to do this is to use the subprocess module.

import subprocess
subprocess.check_call(['iptables', '-t', 'nat', '-A',
                       'PREROUTING', '-p', 'tcp', 
                       '--destination-port', '80',
                       '-j', 'REDIRECT', '--to-port', '8080'])

Note that this method also does not use a shell, which is unnecessary overhead.

As a general rule, you'd better use python bindings whenever possible (better Exception catching, among other advantages.)

For the echo command, it's obviously better to use python to write in the file as suggested in @jordanm's answer.

For the iptables command, maybe python-iptables (PyPi page, GitHub page with description and doc) would provide what you need (I didn't check your specific command).

This would make you depend on an external lib, so you have to weight the benefits. Using subprocess works, but if you want to use the output, you'll have to parse it yourself, and deal with output changes in future iptables versions.

You can use os.system(), like this:

import os
os.system('ls')

Or in your case:

os.system('echo 1 > /proc/sys/net/ipv4/ip_forward')
os.system('iptables -t nat -A PREROUTING -p tcp --destination-port 80 -j REDIRECT --to-port 8080')

Better yet, you can use subprocess's call, it is safer:

from subprocess import call
call('ls')

https://docs.python.org/2/library/subprocess.html

The quickest way:

import os
os.system("your command here")

This isn't the most flexible approach; if you need any more control over your process than "run it once, to completion, and block until it exits", then you should use the subprocess module instead.