import sys
import ast

def evaulate_expressions_in_a_file(filename = "expr_ex.py"):
    """
    Opens a file and prints each line prefixed with its line number.

    Args:
        filename (str): The path to the file to be read.
    """
    try:
        with open(filename, 'r') as file:
            for line_number, line in enumerate(file, start=1):
                # rstrip() removes trailing whitespace, including newline characters,
                # preventing double newlines in the output.
                expr = line.lstrip().rstrip()
                if expr[0] == '#':
                    print(expr)
                else:
                    exec(expr)
                    try:
                        tree = ast.parse(expr, mode='eval')
                        print(f"[line {line_number}] {expr}: {eval(expr)}")
                    except:
                        print(expr)
    except FileNotFoundError:
        print(f"Error: The file '{filename}' was not found.")
    except Exception as e:
        print(f"An unexpected error occurred: {e}")

# usage: python eval.exp.py input_python_expression_filename
if __name__ == "__main__":
    if len(sys.argv) > 1:
        evaulate_expressions_in_a_file(sys.argv[1]) 
    else:
        infile = "expr_ex.py"  # Replace with your desired filename
        evaulate_expressions_in_a_file(infile)