5.10. Fix Operation File

You need to fix files that have some operations written in them and return their results.

Write a function named fix_operation_file which gets two inputs as string, the input and output file names, respectively. The input file will be consisting of some basic operations, such that integers and operators are written line by line instead of a single line. For example, the operation 3+5 becomes 3, +, 5 and written in 3 lines in the input file (see Sample I/O below). Your function should read the input file, and write the operations in a fixed form (3+5 in this example) to the output file and return the results of these operations in a list ([8] in this example).

Note that the input file can contain more than 1 operation. You can assume that the input file will end with a newline character (*:raw-latex:n*), and each of the consecutive 3 lines will represent an operation.

The operators might be basic arithmetic operators as one of '+', '-', '*', '/'.

Hint: While reading the input file line by line, you can use the rstrip() method to get rid of the newline character '\n'. Also you might consider using eval() function for the calculating the result part.

Sample I/O:

Sample function call:
  fix_operation_file("input.txt", "output.txt")

Content of the file "input.txt":
  3
  +
  5
  6
  *
  7
  2
  /
  1
  18
  -
  9


Content of the file "output.txt" after function call:
  3+5
  6*7
  2/1
  18-9


Return value:
  [8, 42, 2.0, 9]

Show the Answer

def fix_operation_file(input_file_name, output_file_name):
  operation_results = []

  # Open files in read and write modes, respectively
  input_file = open(input_file_name, "r")
  output_file = open(output_file_name, "w")
  count = 0
  operation_string = ""

  # Read lines from input file
  for line in input_file:
    # Add the number or operator to operation string to save
    # Get rid of the new line character
    operation_string += line.rstrip("\n")

    count += 1

    # If an operation is read completely
    if count == 3:
      output_file.write(operation_string)
      output_file.write("\n")

      # Use eval to evaluate the operation in operation string
      operation_results.append(eval(operation_string))

      # Reset the count and operation string
      count = 0
      operation_string = ""

  # closing the files
  input_file.close()
  output_file.close()

  return operation_results