Python script for reading from file and display an output

Question

Wrote a python script that reads from a file input.txt

input.txt

    2                     //number of test cases
    2 4                   //testcase 1 ->'2' is size of 1st array and 4 is size of 2nd array
    6 10 6 7 8 9          //testcase 1 -> 1st array is [6,10] and 2nd array is [6,7,8,9]
    1 3                   //testcase 2 ->'1' is size of 1st array and 3 is size of 2nd array
    7 7 8 14              //testcase 2 -> 1st array is [7] and 2nd array is [7,8,14]

The 1st line in the file indicates number of test cases. In this example, we have 2 test cases. Each test case have 2 lines to process - in which first line indicates size of 1st array and size of 2nd array. 2nd line indicates the both array details.

ie, In above example, line 2 indicates size of 1st array and 2nd array for testcase1. line 3 indicates 2 arrays in mentioned sizes for testcase1.line 4 indicates size of 1st array and 2nd array for testcase2. line 5 indicates 2 arrays in mentioned sizes for testcase2.

I need to check whether the elements of 1st array is present in the 2nd one for each test cases. I wrote below program, but that will execute only for 1 test case(ie, I'm checking 2nd and 3rd line manually by giving the check i == 0)

from itertools import islice

def search(arr, element):
    for i in range(len(arr)):
        if int(arr[i]) == int(element):
            return "yes"
        return "no"

f = open("output.txt", "w")

with open("input.txt") as y_file:
    count = y_file.readline()
    if(count > 0):
        for i, line in enumerate(y_file):
            if(i == 0):
                num, size = line.split()
                split_list = [int(num), int(size)]
            if(i == 1):
                temp = iter(line.split())
                res = [list(islice(temp, 0, ele)) for ele in split_list]

    for i in range(len(res[0])):
        result = search(res[1], res[0][i])
        f.write("The result is : " + str(result) + "\n")

f.close()

Can anyone please help me in this?

output will be like

The result is : yes
The result is : no
The result is : yes

That helps to search right? program will work for only 1 test case. ie, it will process 2nd and 3rd line only. What I want is in case of more than 1 test cases, I have to process 4th, 5th ... lines. currently I'm checking if(i == 0) -> instead of this one is there any way to check each line? — Futuregeek
– Futuregeek, Commented Dec 25, 2020 at 4:27
modified the question with expected output. in case of testcase1, it will print The result is : yes The result is : no (in the array [6,7,8,9] -> 6 is present and 10 is not .. incase of testcase 2, it will print The result is : yes (in the array [7,8,14] -> 7 is present ) — Futuregeek
– Futuregeek, Commented Dec 25, 2020 at 4:40
Do you need to check for errors in the input file? For example missing lines? Lines that don't have enough values for the arrays? — MYousefi
– MYousefi, Commented Dec 25, 2020 at 4:43

MYousefi · Accepted Answer · 2020-12-25 05:11:04Z

I would read the file line by line and process.

# read a line and convert to int() for num_cases.
for i in range(0, 2 * num_cases, 2):
  # read a line for split_list
  # check length of split_list
  # read a line for list values all_nums
  # check length of all_nums to be equal to sum of split_list
  # split the list into arr1 and arr2.
  # You can use slicing notation.
  # For example:
  # arr[:5] are the first 5 elements of arr. i.e. indexes 0, 1, 2, 3, 4
  # arr[:-5] are the last 5 elements of arr. i.e. indexes len(arr) - 5, ... , len(arr) - 1
  # arr[5:] are elements 5 and on from arr. i.e. indexes 5, 6, ...
  for value in arr1:
    if value in arr2:
      # output
    else:
      # output

The function int(x) will raise ValueError when input is bad.

Checking the length of the lists allows you to make sure you get the expected number of values on each line.

If the file runs out of lines, readline() will return an empty string which results in a list with length 0 when you split and should fail the length checks.

You can use try, catch to write code to handle the errors such as ValueError from int().

Nanthakumar J J · Accepted Answer · 2020-12-25 04:23:59Z

0

Try this

first_array=[1,2,3]
sec_array=[4,5,3]
print(any(i in sec_array for i in first_array)) # prints True

answered Dec 25, 2020 at 4:23

Nanthakumar J J

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2 Comments

Futuregeek Over a year ago

Thanks for you help. Search function I can modify with this. what I have to do is process through all the lines in a file regarding the first line(if first line =2, there are 2 test cases. I have to process though the lines {2, 3} and {4, 5} in this case.

MYousefi Over a year ago

Your if statements namely if i == 0 and if i == 1 are looking explicitly at first 2 lines it reads. You can change them to if i % 2 == 0 and if i % 2 == 1 to look at even and odd numbered lines.

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