Question

I know it’s a very basic question but i am also a newbie in python environment. I am writing my first program (Data structure problem) where i need to read some input test cases.

Input:

The first line contains the number of test cases T. T test cases follow. 
The first line for each case contains N, the number of elements to be sorted. 
The next line contains N integers a[1],a[2]...,a[N].

Constraints:

1 <= T <= 5
1 <= N <= 100000
1 <= a[i] <= 1000000

Sample Input:

2
5
1 1 1 2 2
5
2 1 3 1 2

I wrote a following program to read the above input from a file but i am sure that this is not the best way to do it because it contains a lot of if-else loop and for loop which will really sucks at the large inputs.

sample = open('sample.txt')
first = sample.readline()
if len(first) > 5 or len(first) <1:
    print "Not correct input";
else:
    test = sample.readline
    for x in range(0,len(first)):
        second = sample.readline()
        if len(second) >100000 or len(second) < 1:
            print "wrong input";
        else:
            third = list()
            for y in range(0, len(third)):
                third.append(sample.readline()[:1])
        method_test(third)  #calling a method for each sample input

Please suggest me the best solution.

Answer 1

This should do it:

with open('sample.txt') as sample:
    num_testcases = int(sample.readline())
    assert 1 <= num_testcases <= 5
    for testcase in range(num_testcases):
        num_elems = int(sample.readline())
        assert 1 <= num_elems <= 10000
        elems = map(int, sample.readline().split())
        assert len(elems) == num_elems
        assert all(1 <= elem <= 100000 for elem in elems)
        method_test(elems)

Edit: Added validity checks.