I have a text file of the format:
2
1 3
2 4
I have written a python program that asks for number of inputs and prints out the values sum .
n = int(raw_input())
for _ in range(n):
a,b = map(int,raw_input().split())
print a+b
But
1 + 2. Shell redirection.
$ python foo.py < input.txt > output.txt
Assuming your input comes from a file, inp.txt, like:
$ cat inp.txt
2
1 3
2 4
You can use the code below, which basically reads the input file line by line, and computes the values and stores them:
with open("inp.txt", "r") as inp, open("out.txt", "w") as out:
no_of_cases = int(inp.readline())
for line in inp:
a,b = map(int,line.split())
out.write("%s\n" % (a + b))
Note that no_of_cases has not been used in the code anywhere above because it is redundant for this example.
This will produce the output file out.txt for you, with following data:
$ cat out.txt
4
6
You can use the fileinput module to make your script support both reading input from a file and reading from stdin.
import fileinput
num_inputs = None
for line in fileinput.input():
if num_inputs is None:
num_inputs = int(line)
else:
a,b = map(int, line.split())
print a+b
This way, if you pass a filename as an argument to your script, it reads from it, else it reads from stdin.
Note that in this snippet I just read all the inputs in file after the first line, and make no real use of the num_inputs variable, but you can easily change that to enforce the expected number of inputs is actually read.
As to writing to a file, this is a basic python question, which has already been answered here.
