Reading multiple raw_inputs

[bindo]

Hello all,

My first post here. Newbie to python and I want to improve the below code mainly for learning purpose. Let me first post it and then explain what how I want to improve it. 

VAR1, VAR2, VAR3= raw_input("Enter ip, port and name seperated by colan").split(":")

template ="""frontend fe:{0}:bind:{1}
        mode tcp
        bind {0}:{1} name {2}"""
 
BLOCK = template.format(VAR1,VAR2,VAR3)
 
with open("file.txt", "a") as myfile:
    myfile.write(BLOCK)

As you can see I'm appending to the "file.txt" based on user inputs. Once the user specify the ip address and the port (i.e: 10.1.2.2:443:somename) it would construct the text in var "template"  sending the correct value to the corresponding "{}". I want to understand the best way to do the following.

-  I want to get the user to specify the raw_input as a command line argument (i.e ./script.py FE-<name>:<ip>:<port>  | BE-<name><ip>:<port>).

-  I want to add another part to the template called "backend bk:<somename>:<someip>:<someport>".  Script should pick up the correct user input to the right section (ie: "FE-<name>:<ip>:<port>" to the "frontend fe" section and "BE-<name><ip>:<port>" to the backend section.

-  once user is done inputting the parameters I want to restart a service i.e:service abc restart. Please note that I want to wait before user adds all the entries before restarting the service. 

Please help out gentleman. I really want to come up to speed.

[nilamo]

string.format() takes arguments, and makes those arguments available to the string via their index. So to add the backend, you could almost literally just copy/paste your frontend section... backend bk:{2}:{0}:{1}

Why are you using var1/var2/var3? Just give them real, meaningful names (maybe ip_addr, port, description?).

- I want to get the user to specify the raw_input as a command line argument (i.e ./script.py FE-<name>:<ip>:<port> | BE-<name><ip>:<port>).

I have no idea what you mean by that. Do you want your script to use command line arguments instead of raw_input()?

- once user is done inputting the parameters I want to restart a service i.e:service abc restart. Please note that I want to wait before user adds all the entries before restarting the service.

# do things
# save things to a file

# restart the service
import os
os.system("service abc restart") # or systemctl restart abc, depending on the flavor of linux

[volcano63]

# restart the service
import os
os.system("service abc restart") # or systemctl restart abc, depending on the flavor of linux

I believe that modern recommendation is to use subprocess module for executing shell commands

[nilamo]

I thought that was only if you wanted to get the result/stdout of the command or if you didn't want to block while it ran, while os.system was fine for fire-and-forget type things?

[snippsat]

while os.system was fine for fire-and-forget type things?

it's not okay to use os.system is deprecated.
There is an exact replacement,but should not be used because of shell=True.

After 3.5 they have named it better subprocess.run,which can be used for most stuff.

[volcano63]

I thought that was only if you wanted to get the result/stdout of the command or if you didn't want to block while it ran, while os.system was fine for fire-and-forget type things?

subprocess module allows a lot of options. You may "fire and forget" - though I am not sure that's a good approach, and if you start a long process without saving reference to process object, how garbage collector will affect it.

You may capture output, redirect it to a pipe, to a file. Send input to process. Get execution results. Though I no longer see threats to discontinue os.system (I believe there were some), I tend to follow recommendations of documentation.

I am also not sure that os.system is "fire-and-forget" thing - if you don't redirect stdout, it will throw it it on your terminal