How do I exit a program if no file is passed?

Question

I have a program that needs input: program.py < test.txt

How would I make it so that the program will exit if it doesn't get a file input?

this is how I read the input:

def file():
    global index
    import sys


    tempo = sys.stdin.readlines()

    for element in tempo:

        if(index == 1):
            key_route.append(element.strip('\n').rstrip().lstrip().lower())
            index = 5
        else:
            routes.append(element.strip('\n').rstrip().lstrip().lower())

Does this answer your question? [How do I check if stdin has some data?](https://stackoverflow.com/questions/3762881/how-do-i-check-if-stdin-has-some-data) — Gino Mempin, May 07 '20 at 00:08

score 0 · Answer 1 · answered May 07 '20 at 00:08

0

test if you have anything in temp:

if not temp: 
    exit()

answered May 07 '20 at 00:08

RickyA

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it doesnt work, it just and waits for input by the looks of things – Julian May 07 '20 at 00:10
and you call `file()`? – RickyA May 07 '20 at 00:16
`sys.stdin.readlines()` might indeed just halts execution until somthing becomes available, which could be none – RickyA May 07 '20 at 00:17
yeah we call file – Julian May 07 '20 at 00:19
you could just ctrl-c it then or take a look at the duplicate question to work around the readlines or you can pass a path to the file as a argument and open it yourself in your program – RickyA May 07 '20 at 00:23

Jackson · Answer 2 · 2020-05-07T00:23:21.203

0

The following should do:

global index
import sys

def file():
    tempo = sys.stdin.readline()

    if not tempo.strip():
        sys.exit()

    for element in tempo:
        if(index == 1):
            key_route.append(element.strip('\n').rstrip().lstrip().lower())
            index = 5
        else:
            routes.append(element.strip('\n').rstrip().lstrip().lower())

file()

Use readline() not readlines()
you need to strip() the var because it will register the '\n' and consider it not empty.

edited May 07 '20 at 00:23

answered May 07 '20 at 00:08

Jackson

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doesn't work, i have updated code to give more context – Julian May 07 '20 at 00:12
@Julian see my modified code. Tested will work. included changes made to your code below my modified code – Jackson May 07 '20 at 00:24
Still doesnt work mate, not sure why :( do you want me to add the whole code? its long – Julian May 07 '20 at 00:27
@Julian it works on my end with the above code. What was the error on your end? – Jackson May 07 '20 at 00:31
dw mate, i fixed it with: if not sys.stdin.isatty(): – Julian May 07 '20 at 00:34

How do I exit a program if no file is passed?

2 Answers2